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Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir Rahmandad 25 th MIT-UAlbany PhD Colloquium, System Dynamics Society Nov 16, 2012
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Page 1: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Using the Method of Simulated Moments (MSM)

for Identification of Dynamic Models

Presenter: Mohammad S. Jalali

Advisor: Dr. Hazhir Rahmandad

25th MIT-UAlbany PhD Colloquium, System Dynamics Society

Nov 16, 2012

Page 2: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Introduction

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 2

Increasingly, dynamic modelers face problems where

estimating model parameters from numerical empirical

data is a requirement.

The field of system dynamics (SD) was ahead of many

approaches available in social sciences in using advanced

analytical methods of the time (Forrester, 1961), and kept

this edge for many years.

For example advanced filtering and estimation methods

were introduced into the SD literature in the 70s (Peterson,

1975).

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 3: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Introduction

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 3

Increasingly, dynamic modelers face problems where

estimating model parameters from numerical empirical

data is a requirement.

The field of system dynamics (SD) was ahead of many

approaches available in social sciences in using advanced

analytical methods of the time (Forrester, 1961), and kept

this edge for many years.

For example advanced filtering and estimation methods

were introduced into the SD literature in the 70s (Peterson,

1975).

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 4: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Introduction

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 4

Increasingly, dynamic modelers face problems where

estimating model parameters from numerical empirical

data is a requirement.

The field of system dynamics (SD) was ahead of many

approaches available in social sciences in using advanced

analytical methods of the time (Forrester, 1961), and kept

this edge for many years.

For example advanced filtering and estimation methods

were introduced into the SD literature in the 70s (Peterson,

1975).

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 5: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Introduction

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 5

However, over the last three decades the research in SD

has largely focused on diverse applications of the original

toolbox, with limited methodological expansions in

parameter estimation domain.

In contrast, research in econometrics and other related

fields have provided many relevant tools over this period

(Greene, 2012).

As a result, currently many studies in SD do not report

formal parameter estimates common in social science

research, or when calibration is pursued, typical measures

of confidence in estimated parameter values are not

reported.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 6: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Introduction

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 6

However, over the last three decades the research in SD

has largely focused on diverse applications of the original

toolbox, with limited methodological expansions in

parameter estimation domain.

In contrast, research in econometrics and other related

fields have provided many relevant tools over this period

(Greene, 2012).

As a result, currently many studies in SD do not report

formal parameter estimates common in social science

research, or when calibration is pursued, typical measures

of confidence in estimated parameter values are not

reported.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 7: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Introduction

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 7

However, over the last three decades the research in SD

has largely focused on diverse applications of the original

toolbox, with limited methodological expansions in

parameter estimation domain.

In contrast, research in econometrics and other related

fields have provided many relevant tools over this period

(Greene, 2012).

As a result, currently many studies in SD do not report

formal parameter estimates common in social science

research, or when calibration is pursued, typical measures

of confidence in estimated parameter values are not

reported.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 8: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Common Techniques

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 8

Modelers typically compare time series data against the

same variables in a model,

and

minimize the weighted sum of a function of the error term

by

changing the uncertain parameters until best fitting

estimates are found through a nonlinear optimization

algorithm (Oliva, 2003).

The error function is frequently defined as the squared

error but absolute error and absolute percent error terms

are also common (Sterman, 2000).

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 9: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Common Techniques

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 9

Modelers typically compare time series data against the

same variables in a model,

and

minimize the weighted sum of a function of the error term

by

changing the uncertain parameters until best fitting

estimates are found through a nonlinear optimization

algorithm (Oliva, 2003).

The error function is frequently defined as the squared

error but absolute error and absolute percent error terms

are also common (Sterman, 2000).

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 10: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Common Techniques

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 10

Weights for different data points are given based on the

confidence the researcher has in the accuracy of the data

and its relevance to the problem at hand.

When reported, confidence intervals are calculated using

normality and independence assumption for error terms

which,

with weights proportional to the reciprocal of error

variance, would turn least squared error estimates into

maximum-likelihood estimates (MLE).

Bootstrapping methods are also sometimes used for

estimating confidence intervals (Dogan, 2007).

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 11: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Common Techniques

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 11

Weights for different data points are given based on the

confidence the researcher has in the accuracy of the data

and its relevance to the problem at hand.

When reported, confidence intervals are calculated using

normality and independence assumption for error terms

which,

with weights proportional to the reciprocal of error

variance, would turn least squared error estimates into

maximum-likelihood estimates (MLE).

Bootstrapping methods are also sometimes used for

estimating confidence intervals (Dogan, 2007).

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 12: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Common Techniques

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 12

Weights for different data points are given based on the

confidence the researcher has in the accuracy of the data

and its relevance to the problem at hand.

When reported, confidence intervals are calculated using

normality and independence assumption for error terms

which,

with weights proportional to the reciprocal of error

variance, would turn least squared error estimates into

maximum-likelihood estimates (MLE).

Bootstrapping methods are also sometimes used for

estimating confidence intervals (Dogan, 2007).

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 13: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Some Challenges

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 13

Challenges with the current parameter estimation

techniques?

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 14: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Some Challenges

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 14

While the common approaches cover many important

estimation challenges, they each include some

shortcomings.

Ad hoc selection of the error term and the weights for

different data points reduces the consistency of the

methods and their ability to provide confidence intervals.

Normality and independence may regularly be violated

which negate the benefits of MLE when using squared

errors.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 15: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Some Challenges

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 15

While the common approaches cover many important

estimation challenges, they each include some

shortcomings.

Ad hoc selection of the error term and the weights for

different data points reduces the consistency of the

methods and their ability to provide confidence intervals.

Normality and independence may regularly be violated

which negate the benefits of MLE when using squared

errors.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 16: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Some Challenges

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 16

While the common approaches cover many important

estimation challenges, they each include some

shortcomings.

Ad hoc selection of the error term and the weights for

different data points reduces the consistency of the

methods and their ability to provide confidence intervals.

Normality and independence may regularly be violated

which negate the benefits of MLE when using squared

errors.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 17: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Some Challenges

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 17

Bootstrapping, while flexible, increases the computational

costs significantly and as a result may prove infeasible for

many realistically-sized problems.

All these methods rely on having time series data, and

cannot extract from distributions in cross-sectional data

the dynamics that have led to those distributions.

Note: Cross-sectional data is data collected at the same point of time.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 18: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Some Challenges

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 18

Bootstrapping, while flexible, increases the computational

costs significantly and as a result may prove infeasible for

many realistically-sized problems.

All these methods rely on having time series data, and

cannot extract from distributions in cross-sectional data

the dynamics that have led to those distributions.

Note: Cross-sectional data is data collected at the same point of time.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 19: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Estimation Procedures’ Requirements

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 19

The following characteristics signify the estimation

procedures ideal for dynamic modelers:

Model Independence: given that most dynamic models

do not follow a fixed structural form (e.g. linearity),

estimation procedures that are independent of model

structure are most beneficial.

Analytical confidence intervals: Ability to find

confidence intervals analytically is important because of

the computational costs of optimizing none-linear dynamic

models and replications needed for bootstrapping

methods.

[4] Soll & Mannes, 2011

[5] Herzog & Hertwig, 2009; Hogarth, 1978; Larrick & Soll, 2006; Lee, Zhang, & Shi, 2011; Rauhut & Lorenz, 2011; Soll &

Larrick, 2009; Wright & Rowe, 2011; Yaniv, 2004a, 2004b

[6] Herzog & Hertwig, 2009; Larrick & Soll, 2006; Soll & Larrick, 2009; Soll & Mannes, 2011

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 20: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Estimation Procedures’ Requirements

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 20

The following characteristics signify the estimation

procedures ideal for dynamic modelers:

Model Independence: given that most dynamic models

do not follow a fixed structural form (e.g. linearity),

estimation procedures that are independent of model

structure are most beneficial.

Analytical confidence intervals: Ability to find

confidence intervals analytically is important because of

the computational costs of optimizing none-linear dynamic

models and replications needed for bootstrapping

methods.

[4] Soll & Mannes, 2011

[5] Herzog & Hertwig, 2009; Hogarth, 1978; Larrick & Soll, 2006; Lee, Zhang, & Shi, 2011; Rauhut & Lorenz, 2011; Soll &

Larrick, 2009; Wright & Rowe, 2011; Yaniv, 2004a, 2004b

[6] Herzog & Hertwig, 2009; Larrick & Soll, 2006; Soll & Larrick, 2009; Soll & Mannes, 2011

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 21: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Estimation Procedures’ Requirements

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 21

The following characteristics signify the estimation

procedures ideal for dynamic modelers:

Model Independence: given that most dynamic models

do not follow a fixed structural form (e.g. linearity),

estimation procedures that are independent of model

structure are most beneficial.

Analytical confidence intervals: Ability to find

confidence intervals analytically is important because of

the computational costs of optimizing none-linear dynamic

models and replications needed for bootstrapping

methods.

[4] Soll & Mannes, 2011

[5] Herzog & Hertwig, 2009; Hogarth, 1978; Larrick & Soll, 2006; Lee, Zhang, & Shi, 2011; Rauhut & Lorenz, 2011; Soll &

Larrick, 2009; Wright & Rowe, 2011; Yaniv, 2004a, 2004b

[6] Herzog & Hertwig, 2009; Larrick & Soll, 2006; Soll & Larrick, 2009; Soll & Mannes, 2011

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 22: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Estimation Procedures’ Requirements

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 22

The Assumption-free error terms: Independence and

distributional assumptions on error terms for dynamic

models are not always easy to justify, so methods with

fewer such assumptions are preferred.

Applicability to diverse data types: including both time

series and cross-sectional data.

No single method fully satisfies all these requirements,

therefore modelers need to choose from a menu of

available estimation methods to match their problem

requirements.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 23: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Estimation Procedures’ Requirements

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 23

The Assumption-free error terms: Independence and

distributional assumptions on error terms for dynamic

models are not always easy to justify, so methods with

fewer such assumptions are preferred.

Applicability to diverse data types: including both time

series and cross-sectional data.

No single method fully satisfies all these requirements,

therefore modelers need to choose from a menu of

available estimation methods to match their problem

requirements.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 24: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Estimation Procedures’ Requirements

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 24

The Assumption-free error terms: Independence and

distributional assumptions on error terms for dynamic

models are not always easy to justify, so methods with

fewer such assumptions are preferred.

Applicability to diverse data types: including both time

series and cross-sectional data.

No single method fully satisfies all these requirements,

therefore modelers need to choose from a menu of

available estimation methods to match their problem

requirements.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 25: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Method of Simulated Moments

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 25

The basic idea of this method is to define appropriate

moments of data and, by changing uncertain parameters,

minimize the difference between those moments and their

simulated counterpart coming from the model.

Moments could be any function of data points available.

However for analytical confidence intervals to be available,

one needs these moments to be normally distributed,

often meaning that:

each moment is an average across a function of multiple

independent observations coming from the same

underlying distribution (then normality follows from the central limit theorem).

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 26: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Method of Simulated Moments

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 26

The basic idea of this method is to define appropriate

moments of data and, by changing uncertain parameters,

minimize the difference between those moments and their

simulated counterpart coming from the model.

Moments could be any function of data points available.

However for analytical confidence intervals to be available,

one needs these moments to be normally distributed,

often meaning that:

each moment is an average across a function of multiple

independent observations coming from the same

underlying distribution (then normality follows from the central limit theorem).

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 27: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Method of Simulated Moments

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 27

The basic idea of this method is to define appropriate

moments of data and, by changing uncertain parameters,

minimize the difference between those moments and their

simulated counterpart coming from the model.

Moments could be any function of data points available.

However for analytical confidence intervals to be available,

one needs these moments to be normally distributed,

often meaning that:

each moment is an average across a function of multiple

independent observations coming from the same

underlying distribution (then normality follows from the central limit theorem).

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 28: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

History of MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 28

McFadden (1989) was the first who proposed using

simulation instead of trying to solve the moment conditions

analytically.

He believes that an unbiased simulator is used in the MSM

where the simulation errors are independent across

observations, and the variance introduced by simulation

will be controlled by the law of large numbers operating

across observations.

Lee (1991) and Duffie (1993) extended the framework and

provided a rigorous treatment of MSM estimators for time-

series and panel-data cases and provided relevant

statistics for making tests.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 29: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

History of MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 29

McFadden (1989) was the first who proposed using

simulation instead of trying to solve the moment conditions

analytically.

He believes that an unbiased simulator is used in the MSM

where the simulation errors are independent across

observations, and the variance introduced by simulation

will be controlled by the law of large numbers operating

across observations.

Lee (1991) and Duffie (1993) extended the framework and

provided a rigorous treatment of MSM estimators for time-

series and panel-data cases and provided relevant

statistics for making tests.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 30: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

History of MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 30

McFadden (1989) was the first who proposed using

simulation instead of trying to solve the moment conditions

analytically.

He believes that an unbiased simulator is used in the MSM

where the simulation errors are independent across

observations, and the variance introduced by simulation

will be controlled by the law of large numbers operating

across observations.

Lee (1991) and Duffie (1993) extended the framework and

provided a rigorous treatment of MSM estimators for time-

series and panel-data cases and provided relevant

statistics for making tests.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 31: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

When to Use MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 31

MSM is best fitted for dynamic modeling problems when

some of the following problem characteristics are present:

Population data:

MSM is suitable for estimation of generic models to

population data. Different units of data such as individuals,

firms, and countries could be available. For each unit one

or more data items (e.g. weight, height, and age for

individual data) could be available.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 32: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

When to Use MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 32

MSM is best fitted for dynamic modeling problems when

some of the following problem characteristics are present:

Population data:

MSM is suitable for estimation of generic models to

population data. Different units of data such as individuals,

firms, and countries could be available. For each unit one

or more data items (e.g. weight, height, and age for

individual data) could be available.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 33: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

When to Use MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 33

Role of random processes:

MSM could be a good choice when models include

stochastic processes that drive the model, and their impact

on the model behavior is reflected in the data against

which the model is to be calibrated, e.g. when we are

trying to match the variance observed across multiple

units.

Confidence Intervals:

MSM would be a suitable choice when analytical

confidence intervals are sought.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 34: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

When to Use MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 34

Role of random processes:

MSM could be a good choice when models include

stochastic processes that drive the model, and their impact

on the model behavior is reflected in the data against

which the model is to be calibrated, e.g. when we are

trying to match the variance observed across multiple

units.

Confidence Intervals:

MSM would be a suitable choice when analytical

confidence intervals are sought.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 35: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

When to Use MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 35

Cross-sectional data:

MSM applies to both cross-sectional and time series data.

Where-as time series data include multiple data points for

the same unit over time, cross-sectional data includes data

points for multiple units at the same time.

MSM may be the only viable choice for estimating dynamic

models when data is cross-sectional as it allows us to

extract the information about the historical trajectories of

units hidden in their cross-sectional distributions.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 36: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

When to Use MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 36

Cross-sectional data:

MSM applies to both cross-sectional and time series data.

Where-as time series data include multiple data points for

the same unit over time, cross-sectional data includes data

points for multiple units at the same time.

MSM may be the only viable choice for estimating dynamic

models when data is cross-sectional as it allows us to

extract the information about the historical trajectories of

units hidden in their cross-sectional distributions.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 37: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 37

Step 1: Choose the Moment Conditions

Usually the first and second moments of model’s

outcomes (mean and variance) are good candidates.

Remember that the number of moment conditions should

be (equal to or) larger than the number of unknown

parameters.

The most informative moments are the ones that

1) Are sensitive to at least one of the unknown

parameters

2) Have rather small variances.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 38: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 38

Step 1: Choose the Moment Conditions

Usually the first and second moments of model’s

outcomes (mean and variance) are good candidates.

Remember that the number of moment conditions should

be (equal to or) larger than the number of unknown

parameters.

The most informative moments are the ones that

1) Are sensitive to at least one of the unknown

parameters

2) Have rather small variances.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 39: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 39

Step 1: Choose the Moment Conditions

Usually the first and second moments of model’s

outcomes (mean and variance) are good candidates.

Remember that the number of moment conditions should

be (equal to or) larger than the number of unknown

parameters.

The most informative moments are the ones that

1) Are sensitive to at least one of the unknown

parameters

2) Have rather small variances.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 40: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 40

Step 1: Choose the Moment Conditions

The right choice of moment conditions is the most crucial

step in identifying the model and recovering model

parameters.

Identification of a model using MSM requires that the

model-generated moment conditions should fit their

empirical counterparts if and only if the structural

parameters equal their true values.

Furthermore, the sufficient condition for identification is a

one-to-one mapping between the structural parameters

and a subset of the moment restrictions of the same

dimension.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 41: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 41

Step 1: Choose the Moment Conditions

The right choice of moment conditions is the most crucial

step in identifying the model and recovering model

parameters.

Identification of a model using MSM requires that the

model-generated moment conditions should fit their

empirical counterparts if and only if the structural

parameters equal their true values.

Furthermore, the sufficient condition for identification is a

one-to-one mapping between the structural parameters

and a subset of the moment restrictions of the same

dimension.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 42: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 42

Step 1: Choose the Moment Conditions

The right choice of moment conditions is the most crucial

step in identifying the model and recovering model

parameters.

Identification of a model using MSM requires that the

model-generated moment conditions should fit their

empirical counterparts if and only if the structural

parameters equal their true values.

Furthermore, the sufficient condition for identification is a

one-to-one mapping between the structural parameters

and a subset of the moment restrictions of the same

dimension.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 43: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 43

Step 1: Choose the Moment Conditions

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

- The moment represented by the dashed–line is not informative.

- It is not very sensitive to changes in parameter value.

- We can not even be sure that these small changes are due to true

response of the model to various parameter value or are the artifact of

computational or sampling errors.

Page 44: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 44

Step 1: Choose the Moment Conditions

Example:

A simple model of individual’s body mass, consisting of fat

mass and fat free mass, is developed by Rahmandad

(2011).

The model included a few uncertain parameters. In

absence of time series data, those parameters were

estimated from cross sectional data on individual weights

coming from the National Health and Nutrition Examination

Survey (NHANES).

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 45: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 45

Step 1: Choose the Moment Conditions

Example:

A simple model of individual’s body mass, consisting of fat

mass and fat free mass, is developed by Rahmandad

(2011).

The model included a few uncertain parameters. In

absence of time series data, those parameters were

estimated from cross sectional data on individual weights

coming from the National Health and Nutrition Examination

Survey (NHANES).

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 46: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 46

Step 1: Choose the Moment Conditions

Example:

NHANES 2005-2006 population of 5,971 subjects was

categorized into 110 subpopulations based on:

different ethnicities (5 ethnicities),

genders (2 genders),

age (11 age groups).

For each population group two moments, average body

weight and variance of body weight, were calculated as

the moments to be matched, leading to a total of 220

moments to match.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 47: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 47

Step 1: Choose the Moment Conditions

Example:

NHANES 2005-2006 population of 5,971 subjects was

categorized into 110 subpopulations based on:

different ethnicities (5 ethnicities),

genders (2 genders),

age (11 age groups).

For each population group two moments, average body

weight and variance of body weight, were calculated as

the moments to be matched, leading to a total of 220

moments to match.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 48: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 48

Step 2: Weighting Matrix

A two-step procedure should be developed to calculate the

optimal weighting matrix (W) (More technical information will be presented

in the forthcoming book chapter.)

The right choice of weighting matrix ensures that we get

the smallest asymptotic variance for our estimated values.

In the simplest case, the identity matrix is used as the

initial value of the weighting matrix in the first step.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 49: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 49

Step 2: Weighting Matrix

A two-step procedure should be developed to calculate the

optimal weighting matrix (W) (More technical information will be presented

in the forthcoming book chapter.)

The right choice of weighting matrix ensures that we get

the smallest asymptotic variance for our estimated values.

In the simplest case, the identity matrix is used as the

initial value of the weighting matrix in the first step.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 50: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 50

Step 2: Weighting Matrix

A two-step procedure should be developed to calculate the

optimal weighting matrix (W) (More technical information will be presented

in the forthcoming book chapter.)

The right choice of weighting matrix ensures that we get

the smallest asymptotic variance for our estimated values.

In the simplest case, the identity matrix is used as the

initial value of the weighting matrix in the first step.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 51: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 51

Step 2: Weighting Matrix

A two-step procedure should be developed to calculate the

optimal weighting matrix (W) (More technical information will be presented

in the forthcoming book chapter.)

The right choice of weighting matrix ensures that we get

the smallest asymptotic variance for our estimated values.

In the simplest case, the identity matrix is used as the

initial value of the weighting matrix in the first step.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 52: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 52

Step 3: Initial Value and Simulation

We need to generate a large sample of model outcome as

the base for estimating model’s moments.

In equilibrium models, it is recommended that we discard

earlier observations (in the time-series sense) since these

observations are sensitive to the initial value of the model

and are not in the steady-state.

If we need observations over time, it is recommended to

generate a vector of simulations and discard the first

observation.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 53: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 53

Step 3: Initial Value and Simulation

We need to generate a large sample of model outcome as

the base for estimating model’s moments.

In equilibrium models, it is recommended that we discard

earlier observations (in the time-series sense) since these

observations are sensitive to the initial value of the model

and are not in the steady-state.

If we need observations over time, it is recommended to

generate a vector of simulations and discard the first

observation.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 54: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 54

Step 3: Initial Value and Simulation

We need to generate a large sample of model outcome as

the base for estimating model’s moments.

In equilibrium models, it is recommended that we discard

earlier observations (in the time-series sense) since these

observations are sensitive to the initial value of the model

and are not in the steady-state.

If we need observations over time, it is recommended to

generate a vector of simulations and discard the first

observation.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 55: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 55

Step 3: Initial Value and Simulation

We need to generate a large sample of model outcome as

the base for estimating model’s moments.

In equilibrium models, it is recommended that we discard

earlier observations (in the time-series sense) since these

observations are sensitive to the initial value of the model

and are not in the steady-state.

If we need observations over time, it is recommended to

generate a vector of simulations and discard the first

observation.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 56: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 56

Step 4: Optimization Routine and Iteration

This is the most computationally-challenging step of MSM

procedure. We need to minimize the weighted distance of

model-generated moments from empirical moments.

N is the number of simulations,

d is the vector of data,

h is the moment function of interest,

yj(B) is the vector of simulated values corresponding to vector d.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

𝛽 = 𝑎𝑟𝑔𝑚𝑖𝑛𝛽∈𝑅𝑘 ℎ 𝑑 −1

𝑁 ℎ 𝑦𝑗 𝛽

𝑁

𝑗=1

.𝑊−1 . ℎ 𝑑 −1

𝑁 ℎ 𝑦𝑗 𝛽

𝑁

𝑗=1

Page 57: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 57

Step 4: Optimization Routine and Iteration

This is the most computationally-challenging step of MSM

procedure. We need to minimize the weighted distance of

model-generated moments from empirical moments.

N is the number of simulations,

d is the vector of data,

h is the moment function of interest,

yj(B) is the vector of simulated values corresponding to vector d.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

𝛽 = 𝑎𝑟𝑔𝑚𝑖𝑛𝛽∈𝑅𝑘 ℎ 𝑑 −1

𝑁 ℎ 𝑦𝑗 𝛽

𝑁

𝑗=1

.𝑊−1 . ℎ 𝑑 −1

𝑁 ℎ 𝑦𝑗 𝛽

𝑁

𝑗=1

Page 58: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 58

Step 4: Optimization Routine and Iteration

We need to use numerical optimization routines to find the

minimum of the total error function. A smart choice of initial

values for parameters may facilitate the quicker

convergence of the optimization routine significantly.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 59: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 59

Step 5: Interpretation and Making Conclusions

The results we will get from previous steps are just a point

estimation of true parameter values. We need to do further

statistical and computational analysis to make sure that

our results are robust and reliable.

The first step is to look at the confidence interval of

estimated values. The confidence interval estimation will

tell us about the range of probable parameter values.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 60: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 60

Step 5: Interpretation and Making Conclusions

The results we will get from previous steps are just a point

estimation of true parameter values. We need to do further

statistical and computational analysis to make sure that

our results are robust and reliable.

The first step is to look at the confidence interval of

estimated values. The confidence interval estimation will

tell us about the range of probable parameter values.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 61: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Recipe for MSM

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 61

Step 5: Interpretation and Making Conclusions

The results we will get from previous steps are just a point

estimation of true parameter values. We need to do further

statistical and computational analysis to make sure that

our results are robust and reliable.

The first step is to look at the confidence interval of

estimated values. The confidence interval estimation will

tell us about the range of probable parameter values.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 62: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Discussions

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 62

Adda (2003) believed that for implementing the MSM, a

large number of simulations is needed to compute the

standard errors of the estimator.

Using Monte-Carlo analysis, Ruge-Murcia (2012)

presented that even when simulated series are short, the

MSM works and it can deliver accurate estimates;

however, the distribution of the estimates is not efficiently

approximated by the asymptotic normal distribution.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 63: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Discussions

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 63

Adda (2003) believed that for implementing the MSM, a

large number of simulations is needed to compute the

standard errors of the estimator.

Using Monte-Carlo analysis, Ruge-Murcia (2012)

presented that even when simulated series are short, the

MSM works and it can deliver accurate estimates;

however, the distribution of the estimates is not efficiently

approximated by the asymptotic normal distribution.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 64: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Discussions

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 64

There are ways to address some of these concerns.

- Providing graphs showing the sensitivity of the

likelihood function to parameter values is one way to

convince the others that the moments were indeed

informative.

- Providing the data (if they are not propriety) and the

programming codes enables others to check the

results independently.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 65: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Discussions

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 65

There are ways to address some of these concerns.

- Providing graphs showing the sensitivity of the

likelihood function to parameter values is one way to

convince the others that the moments were indeed

informative.

- Providing the data (if they are not propriety) and the

programming codes enables others to check the

results independently.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 66: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Discussions

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 66

There are ways to address some of these concerns.

- Providing graphs showing the sensitivity of the

likelihood function to parameter values is one way to

convince the others that the moments were indeed

informative.

- Providing the data (if they are not propriety) and the

programming codes enables others to check the

results independently.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 67: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Discussions

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 67

MLE requires distributional assumptions on error terms.

When such assumptions are justified (either empirically,

based on the observed error, or based on theoretical

considerations), MLE provides a more efficient estimation

method than MSM.

When error terms do not follow any well-established

distribution, MSM may be a better choice.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 68: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Discussions

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 68

MLE requires distributional assumptions on error terms.

When such assumptions are justified (either empirically,

based on the observed error, or based on theoretical

considerations), MLE provides a more efficient estimation

method than MSM.

When error terms do not follow any well-established

distribution, MSM may be a better choice.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 69: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Discussions

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 69

MSM provides a large degrees freedom for choosing the

moment conditions which serve the interests of the

modeler.

By imposing different moment conditions one may recover

different structural parameters and as long as there are

enough meaningful moment conditions the researcher has

the luxury of using an arbitrary subset of moments.

This critic compares MSM method to standard

econometrics techniques which is more easily available for

outsiders and provide a better chance of independent

verification of the estimation results.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 70: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Discussions

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 70

MSM provides a large degrees freedom for choosing the

moment conditions which serve the interests of the

modeler.

By imposing different moment conditions one may recover

different structural parameters and as long as there are

enough meaningful moment conditions the researcher has

the luxury of using an arbitrary subset of moments.

This critic compares MSM method to standard

econometrics techniques which is more easily available for

outsiders and provide a better chance of independent

verification of the estimation results.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 71: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

Discussions

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 71

MSM provides a large degrees freedom for choosing the

moment conditions which serve the interests of the

modeler.

By imposing different moment conditions one may recover

different structural parameters and as long as there are

enough meaningful moment conditions the researcher has

the luxury of using an arbitrary subset of moments.

This critic compares MSM method to standard

econometrics techniques which is more easily available for

outsiders and provide a better chance of independent

verification of the estimation results.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 72: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

References

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 72

• Adda, J., & Cooper, Russell W. (2003). Dynamic economics : quantitative methods and applications.

Cambridge, Mass.: MIT Press.

• Dogan, G. (2007). Bootstrapping for confidence interval estimation and hypothesis testing for parameters

of system dynamics models. System Dynamics Review, 23(4), 415-436.

• Duffie, D., & Singleton, K. J. (1993). Simulated Moments Estimation of Markov-Models of Asset Prices.

Econometrica, 61(4), 929-952.

• Forrester, Jay W. (1961). Industrial Dynamics (1 ed.). Cambridge: The M.I.T. Press.

• Greene, William H. (2012). Econometric analysis (7th ed.). Boston: Prentice Hall.

• Lee, Bong-Soo, & Ingram, Beth Fisher. (1991). Simulation estimation of time-series models. Journal of

Econometrics, 47(2–3), 197-205. doi: 10.1016/0304-4076(91)90098-X

• Mcfadden, D. (1989). A Method of Simulated Moments for Estimation of Discrete Response Models

without Numerical-Integration. Econometrica, 57(5), 995-1026.

• Oliva, R. (2003). Model calibration as a testing strategy for system dynamics models. European Journal

of Operational Research, 151(3), 552-568. doi: Doi 10.1016/S0377-2217(02)00622-7

• Peterson, D.W. (1975). Hypothesis, estimation, and validation of dynamic social models- Energy demand

modeling. (Ph.D.), Massachusetts Institute of Technology, Cambridge, MA.

• Rahmandad, H., & Sabounchi, N. (2011). Building and estimating a dynamic model of weight gain and

loss for individuals and populations. Paper presented at the the 29th International Conference of the

System Dynamics Society, Washington, DC.

• Ruge-Murcia, Francisco. (2012). Estimating nonlinear DSGE models by the simulated method of

moments: With an application to business cycles. Journal of Economic Dynamics and Control, 36(6), 914-

938. doi: 10.1016/j.jedc.2012.01.008

• Sterman, John. (2000). Business dynamics: systems thinking and modeling for a complex world (1 ed.).

Boston: McGraw-Hill/Irwin.

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions

Page 73: Using the Method of Simulated Moments (MSM) for ...Using the Method of Simulated Moments (MSM) for Identification of Dynamic Models Presenter: Mohammad S. Jalali Advisor: Dr. Hazhir

25th MIT-UAlbany System Dynamics Ph.D. Colloquium, Nov 2012 Slide: 73

Thank you!

Any suggestion?

mj @ vt . edu

Contents:

- Introduction

- Common

Techniques

- Some

Challenges

- Estimation

Procedures’

Requirements

- MSM

- History of

MSM

- When to Use

MSM

- Recipe for

MSM

- Discussions


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