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Lane County 20-Year Coordinated Population Forecast Project
Kick-off Public MeetingDecember 2, 2008
Population Forecasting Techniques
Presentation by Population Research Center
Project Team
Population Research Center Project Team
Risa Proehl, Project LeadDanan Gu, Demographic Analyst
Ken Radin, GIS AnalystGeorge C. Hough Jr., Director
Population ForecastsProcess
Develop Demographic Models Using Historic and Recent Data
Analyze Past and Recent Population Trends - Reasons for Change, Continuous or Short-term?
Gather Information About Recent and Planned Future Housing and Population change (housing developments, construction of new GQ facilities, new employers)
Make Assumptions About Future Housing and Population Change
Revise Forecasts on a Regular Basis
Outline
Population Trends – Lane CountyPopulation Projection MethodsAssumptions About the Future
Population Change in Lane County
Lane County Grew Consistently 1900 to 2008 Lane County Grew in Absolute and Relative
Reflecting Societal/Economic Conditions Lane County Population Change Has Shifted from
High Growth Scenario of 3% per year to about 1% per annum
The Eugene and Springfield Shares of County Population Increased but Have Become More Stable in Recent Years
Lane County Grew Consistently Over the Past Century
Population Change 1900 to 2008 Reflects Decade Economic Changes
Higher Growth and Lower Growth Periods
City Population Shares Have Stabilized Over Recent Times
Population Projection TechniquesPrimary Models for this Study
COHORT-COMPONENT METHODfor Lane County, Eugene, SpringfieldRelies on Age-Sex Schedules of Demographic BehaviorPopulation Pyramid Displays Age StructureMortality – Fairly Constant over TimeFertility – Decreased Teen Fertility, Older Mothers and
Latino BirthsMigration – In Lane Co., Mostly Influenced by Common
College Pattern and Employment AvailabilityMigration Rates Subject to Greater Fluctuation than
Mortality and Fertility and more unpredictableThree Scenarios of Growth: High, Medium, Low
0-4
5-9
10-14
15-19
20-24
25-29
30-34
35-39
40-44
45-49
50-54
55-59
60-64
65-69
70-74
75-79
80-84
85+
-20000 -15000 -10000 -5000 0 5000 10000 15000 20000
Population Distribution, Lane County, 1990 and 2000
Males Females
-20000 -15000 -10000 -5000 0 5000 10000 15000 20000
0-45-9
10-1415-1920-2425-2930-3435-3940-4445-4950-5455-5960-6465-6970-7475-7980-84
85+
1990
2000
Population
Age Schedules of Fertility, Mortality and Migration Determine the Age Structure of a Population
Age Schedules of Fertility, Mortality and Migration Determine the Age Structure of a Population
Mortality Age Schedules Are Similar for 1990 and 2000
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0 1--4 5--14 15-24 25-34 35-44 45-54 55-64 65-74 75-84 85+
1990 2000
Deat
h ra
te
Age
Fertility Schedules Are Similar for 1990 and 2000
Migration Schedules Show Dominance of College Migration
Population Projection TechniquesPrimary Models for this Study, con’t.HOUSING UNIT METHODfor Ten Smaller Cities, Unincorporated Area, Area Outside UGBs
Housing Unit Growth – Trend Actual, Trend County SharesHousing Unit Type (single-/multi-family)Household Composition – PersonsPersons Per HouseholdOccupancy RatesAdd Group Quarters PopulationBased on Medium Growth Scenario – one scenario as smaller areas have more variability than larger areasControlled to Cohort-Component Model Results for County
Housing Unit Method, con’t.
Fluctuations in housing unit growth follows economic trends with Exceptions
PPH Factors that influence PPH:
Race/Ethnicity, Age (fertility), Economy
Generally Decreasing in U.S. Occupancy Rates - Seasonal Housing
Ranges from 79% to 95% Group Quarters Population Ranges from
0% to 5% of Total Population Doesn’t Fluctuate Greatly (unless
new facility built or closed)
Average Annual Number of Housing Units Added
0
20
40
60
80
100
120
140
160
COTTAGE GROVE FLORENCE
1970s 1980s 1990s 2000-08
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
EUGENE SPRINGFIELD UNINCORP
1970s 1980s 1990s 2000-08
0
10
20
30
40
50
60
70
80
90
CRESWELL DUNES CITY JUNCTION CITY OAKRIDGE VENETA
1970s 1980s 1990s 2000-08
0
1
2
3
4
5
6
7
8
9
10
COBURG LOWELL WESTFIR
1970s 1980s 1990s 2000-08
Housing Unit Method, con’t.
PPH 1990 2000 2007
COBURG 2.41 2.64
COTTAGEGROVE 2.60 2.54
CRESWELL 2.68 2.76
DUNES CITY 2.30 2.23
EUGENE 2.30 2.27 2.25
FLORENCE 2.21 2.02
JUNCTIONCITY 2.42 2.55
LOWELL 2.90 2.72
OAKRIDGE 2.45 2.35
SPRINGFIELD 2.54 2.54
VENETA 2.79 2.85
WESTFIR 2.84 2.76
UNINCORP 2.69 2.58
LANE CO 2.49 2.42 2.41
2000Occ. Rate GQ
COBURG 95% 0
COTTAGE GROVE 95% 152
CRESWELL 95% 58
DUNES CITY 79% 0
EUGENE 95% 6,078
FLORENCE 85% 56
JUNCTION CITY 95% 138
LOWELL 92% 0
OAKRIDGE 88% 0
SPRINGFIELD 95% 635
VENETA 95% 0
WESTFIR 94% 0
UNINCORP 93% 302
LANE CO 94% 7,418
Population Projection Techniques
For Comparison and to Serve as a CheckShift-Share and Other Ratio MethodsTrend ExtrapolationSimple Economic/Employment ModelLand Use and CapacityAdditional Housing Unit Models (in addition to CC
models)
Other Models/Techniques to Considerfor All Areas in this Study
Data
Background Information Some Entered Directly into Projection Models Some Provide Support for Assumptions Made for
Future Change All Data Available for Lane County, Many Available
for Individual Cities (Census, Land Use, Housing, Births, Group Quarters Population)
Data Data Sources
1990 and 2000 Census Data ACS Data – post-2000 Vital Statistics Building Permit Data Annual Housing and Population Data from Local Jurisdictions PRC Annual Population Estimates, post-2000; Revised to
Current Boundaries and UGBs School Enrollment Data Land Use Data and Plans for Future Development Local Studies – e.g., School Enrollment Projections, Previous
Coordinated Plans, TSP Employment and Labor Force Data and Projections Previous OEA/DAS–County Projections to 2040 Confer with OEA about Current and Revised Forecast Information from local Government Staff, Public Meetings
Future Conditions and Considerations
Assumptions are Based on Past and Recent Trends, Occurrence of Events, and Plans for Future Housing
Future Assumptions for Lane County? Mortality – Slight Increase in Longevity Fertility – Slightly Older Mothers and Latino Births Migration – Employment and Group Quarters
Populations Assumptions about PPH, Vacancy Rates, Housing
Construction Some Current Conditions are Assumed to be the Same
in Future (e.g. land use zoning, residential densities, UGBs expand as needed)
Citizen and Governmental Input Combined with Demographic Expertise Will Produce the Most Reasonable or Likely Forecasts
High: Assuming average annual increase rate from 1970-2005.Medium: Assuming average annual increase rate from 1990-2005.Low: Assuming average annual increase rate from 2000-2005. (Ann. Time Series)
Life Expectancy, Lane County, 1970-2035
Estimates after 2005
Total Fertility Rate, Lane County, 1990-2035
Mean age at births, Lane County,1970-2035
Population Growth, Net Migration, Lane County, 1980-2005Population Growth, Net Migration, Lane County, 1980-2005
Pop
ula
tion
Pop
ula
tion
Net
mig
rate
rate
( p
er
1,0
00)
Net
mig
rate
rate
( p
er
1,0
00)
YearYear
Projections and ForecastsGeneral Comments
Projections Are More Accurate in Short-Term The Larger the Geographic Area, The More Accurate
the Projection Population Forecast is a Tool to Help with Planning and
Serves as a Guide – not a Guarantee of What Will Occur
Revisions to Forecasts Should be Made Regularly! PRC Utilizes Best Practices – Professional Associations