Multivariate Causality Tests with Simulation and
Application
Zhidong Bai
School of Mathematics and Statistics, Northeast Normal University
Department of Statistics and Applied Probability,
National University of Singapore
Heng Li
Department of Mathematics
Hong Kong Baptist University
Wing-Keung Wong
Department of Economics
Hong Kong Baptist University
Bingzhi Zhang
Department of BioStatistics
Columbia University
Corresponding author: Wing-Keung Wong, Department of Economics, Hong Kong Bap-
tist University, Kowloon Tong, Hong Kong. Tel: (852)-3411-7542, Fax: (852)-3411-5580,
Email: [email protected]
Acknowledgments The third author would like to thank Professors Robert B. Miller
and Howard E. Thompson for their continuous guidance and encouragement. This re-
search is partially supported by Northeast Normal University, the National University of
Singapore, Hong Kong Baptist University, and Columbia University.
Multivariate Causality Tests with Simulation and
Application
Abstract The traditional linear Granger causality test has been widely used to ex-
amine the linear causality among several time series in bivariate settings as well as mul-
tivariate settings. Hiemstra and Jones (1994) develop a nonlinear Granger causality test
in a bivariate setting to investigate the nonlinear causality between stock prices and trad-
ing volume. In this paper, we first discuss linear causality tests in multivariate settings
and thereafter develop a nonlinear causality test in multivariate settings. A Monte Carlo
simulation is conducted to demonstrate the superiority of our proposed multivariate test
over its bivariate counterpart. In addition, we illustrate the applicability of our proposed
test to analyze the relationships among different Chinese stock market indices.
Keywords: linear Granger causality, nonlinear Granger causality, U-statistics, simu-
lation, stock markets.
JEL Classification:
C01, C12, G10
Linear and Nonlinear Causality Tests 1
1 Introduction
It is an important issue to detect the causal relation among several time series and it starts
with two series, see, for example, Chiang, et al (2010) and Qiao, et al (2008, 2009) and
the references therein for more discussion. To examine whether past information of one
series could contribute to the prediction of another series, linear Granger causality test
(Granger, 1969) is developed to examine whether lag terms of one variable significantly
explain another variable in a vector autoregressive regression model.
Linear Granger causality test can be used to detect the causal relation between two
time series.1 However, the linear Granger causality test does not perform well in detecting
nonlinear causal relationships. To circumvent the limitation, Baek and Brock (1992)
develop a bivariate nonlinear Granger causality test to examine the remaining nonlinear
predictive power of a residual series of a variable on the residual of another variable
obtained from a linear model. Hiemstra and Jones (1994) have further modified the test.
Nevertheless, the multivariate causal relationships are important but it has not been well-
studied, especially for nonlinear causality relationship. Thus, it is important to extend
the Granger causality test to nonlinear causality test in the multivariate settings.
In this paper, we first discuss linear causality tests in multivariate settings and there-
after extend the theory by developing a nonlinear causality test in the multivariate setting.
For any n variables involved in the causality test, we discuss a n-equation vector autore-
gressive regression (VAR) model to conduct the linear Granger causality test, and test
for the significance of relevant coefficients across equations using likelihood ratio test. If
those coefficients are significantly different from zero, the linear causality relationship is
identified. We then extend the nonlinear Granger causality test from bivariate setting
to multivariate setting. We notice that the bivariate nonlinear Granger causality test
is developed by mainly applying the properties of U-statistic developed by Denker and
1See, for example, Wong, et al (2006), Qiao, et al (2007), Chen, et al (2008), and Foo, et al (2008).
Linear and Nonlinear Causality Tests 2
Keller (1983, 1986). Central limit theorem can be applied to the U-statistic whose argu-
ments are strictly stationary, weakly dependent and satisfy mixing conditions of Denker
and Keller (1983, 1986). When we extend the test to the multivariate settings, we find
that the properties of the U-statistic for the bivariate settings could also be used in the
development of our proposed test statistic in the multivariate settings, which is also a
function of U-statistic.
The paper is organized as follows. We begin in next section by introducing definitions
and notations and stating some basic properties for the the linear and nonlinear Granger
causality tests to test for linear and nonlinear Granger causality relationships between two
series. In Section 3, we first discuss the linear Granger causality tests in the multivariate
settings and thereafter develop the nonlinear Granger causality tests in the multivariate
settings. In Section 4, we conduct simulation to demonstrate the superiority of our pro-
posed multivariate test over its bivariate counterpart in the performance of both size and
power. In Section 5, we illustrate the applicability of our proposed test to analyze the
relationships among different Chinese stock market indices. Section 6 gives a summary
of our paper.
2 Bivariate Granger Causality Test
In this section, we will review the definitions of linear and nonlinear causality and discuss
the linear and nonlinear Granger causality tests to identify the causality relationships
between two variables.
2.1 Bivariate Linear Granger Causality Test
The linear Granger causality is conducted based on the following two-equation model:
Linear and Nonlinear Causality Tests 3
Definition 2.1. In a two-equation model:
xt = a1 +
p∑i=1
αixt−i +
p∑i=1
βiyt−i + ε1t (1a)
and
yt = a2 +
p∑i=1
γixt−i +
p∑i=1
δiyt−i + ε2t , (1b)
where all {xt} and {yt} are stationary variables, p is the optimal lag in the system, and
ε1t and ε2t are the disturbances satisfying the regularity assumptions of the classical linear
normal regression model. The variable {yt} is said not to Granger cause {xt} if βi = 0
in (1a), for any i = 1, · · · , p. In other words, the past values of {yt} do not provide any
additional information on the performance of {xt}. Similarly, {xt} does not Granger
cause {yt} if γi = 0 in (1b), for any i = 1, · · · , p.
It is well-known that one can test for linear causal relations between {xt} and {yt} by
testing the following null hypotheses separately:
H10 : β1 = · · · = βp = 0, and H2
0 : γ1 = · · · = γp = 0.
From testing these hypotheses, we have four possible testing results:
(a) If both Hypotheses H10 and H2
0 are accepted, there is no linear causal relationship
between {xt} and {yt}.
(b) If Hypothesis H10 is accepted but Hypothesis H2
0 is rejected, then there exists linear
causality running unidirectionally from {xt} to {yt} .
(c) If Hypothesis H10 is rejected but Hypothesis H2
0 is accepted, then there exists linear
causality running unidirectionally from {yt} and {xt} .
(d) If both Hypotheses H10 and H2
0 are rejected, then there exist feedback linear causal
relationships between {xt} and {yt}.
Linear and Nonlinear Causality Tests 4
There are several statistics could be used to test the above hypotheses. One of the
most commonly used statistics is the standard F -test. To test the hypothesis H10 : β1 =
· · · = βp = 0 in (1a), the sum of squares of the residuals from both the full regression,
SSRF , and the restricted regression, SSRR, are computed in the equation (1a) and the
F -test follows
F =(SSRR − SSRF )/p
SSRF /(n− 2p− 1), (1)
where p is the optimal number of lag terms of yt in the regression equation on xt and n is
the number of observations. If {yt} does not Granger cause {xt}, F in (1) is distributed
as F(p,n−2p−1). For any given significance level α, we reject the null hypothesis H10 if
F exceeds the critical value Fα (p,n−2p−1). Similarly, one could test for the second null
hypothesis H20 : γ1 = · · · = γp = 0, and identify the linear causal relationship from {xt}
to {yt}.
2.2 Bivariate Nonlinear Granger Causality Test
The general test for nonlinear Granger causality is first developed by Baek and Brock
(1992) and, later on, modified by Hiemstra and Jones (1994). As the linear Granger
causality test is inefficient in detecting any nonlinear causal relationship, to examine the
nonlinear Granger causality relationship between a pair of series, say {xt} and {yt}, one
has to first apply the linear models in (1a) and (1b) to {xt} and {yt} for identifying
their linear causal relationships and obtain their corresponding residuals, {ε1t} and {ε2t}.Thereafter, one has to apply a nonlinear Granger causality test to the residual series, {ε1t}and {ε2t}, of the two variables, {xt} and {yt}, being examined to identify the remaining
nonlinear causal relationships between their residuals.
We first state the definition of nonlinear Granger causality as follows:
Definition 2.2. For any two strictly stationary and weakly dependent series {Xt} and
Linear and Nonlinear Causality Tests 5
{Yt}, the m-length lead vector of Xt is given by
Xmt ≡ (
Xt, Xt+1, · · · , Xt+m−1
), m = 1, 2, · · · , t = 1, 2, · · ·
and Lx-length lag vector of Xt is defined as
XLxt−Lx
≡ (Xt−Lx , Xt−Lx , · · · , Xt−1
), Lx = 1, 2, · · · , t = Lx + 1, Lx + 2, · · · .
The m-length lead vector, Y mt and the Ly-length lag vector, Y
Ly
t−Ly, of Yt can be defined sim-
ilarly. Series {Yt} does not strictly Granger cause another series {Xt} nonlinearly
if and only if:
Pr(‖Xm
t −Xms ‖ < e
∣∣∣‖ XLxt−Lx
−XLxs−Lx
‖< e, ‖ YLy
t−Ly− Y
Ly
s−Ly‖< e
)
=Pr(‖Xm
t −Xms ‖ < e
∣∣‖ XLxt−Lx
−XLxs−Lx
‖< e)
,
where Pr(· | · ) denotes conditional probability and ‖ · ‖ denotes the maximum norm which
is defined as
‖X − Y ‖ = max(|x1 − y1|, |x2 − y2|, · · · , |xn − yn|
),
for any two vectors X =(x1, · · · , xn
)and Y =
(y1, · · · , yn
).
Under Definition 2.2, the nonlinear Granger causality test statistic is given by
√n
(C1
(m + Lx, Ly, e, n
)
C2
(Lx, Ly, e, n
) − C3
(m + Lx, e, n
)
C4
(Lx, e, n
))
, (2)
where
Linear and Nonlinear Causality Tests 6
C1
(m + Lx, Ly, e, n
) ≡ 2
n(n− 1)
∑∑t<s
I(xm+Lx
t−Lx, xm+Lx
s−Lx, e
) · I(y
Ly
t−Ly, y
Ly
s−Ly, e
),
C2
(Lx, Ly, e, n
) ≡ 2
n(n− 1)
∑∑t<s
I(xLx
t−Lx, xLx
s−Lx, e
) · I(y
Ly
t−Ly, y
Ly
s−Ly, e
),
C3
(m + Lx, e, n
) ≡ 2
n(n− 1)
∑∑t<s
I(xm+Lx
t−Lx, xm+Lx
s−Lx, e
),
C4
(Lx, e, n
) ≡ 2
n(n− 1)
∑∑t<s
I(xLx
t−Lx, xLx
s−Lx, e
), and
I(x, y, e) =
0, if ‖x− y‖ > e
1, if ‖x− y‖ ≤ e.
The test statistic, see Hiemstra and Jones (1994), possesses the following property:
Theorem 2.1. For given values of m, Lx, Ly and e > 0 defined in Definition 2.2,
under the assumptions that {Xt}, {Yt} are strictly stationary, weakly dependent, and sat-
isfy the conditions stated in Denker and Keller (1983), if {Yt} does not strictly Granger
cause {Xt}, then the test statistic defined in (2) is distributed as N(0, σ2(m,Lx, Ly, e)
)
asymptotically, and the estimator of the variance σ2(m,Lx, Ly, e) is given by
σ2(m,Lx, Ly, e
)= dT · Σ · d ,
where
d =
[1
C2
(Lx, Ly, e, n
) ,−C1
(m + Lx, Ly, e, n
)
C22
(Lx, Ly, e, n
) ,− 1
C4
(Lx, e, n
) ,C3
(m + Lx, e, n
)
C24
(Lx, e, n
)]T
and Σ is a matrix containing elements
Σi,j = 4 ·K(n)∑
k=1
ωk(n)
[1
2(n− k + 1)
∑t
(Ai,t(n) · Aj,t−k+1(n) + Ai,t−k+1(n) · Aj,t(n)
)],
in which K(n) = [n1/4], [x] is the integer part of x,
Linear and Nonlinear Causality Tests 7
ωk(n) =
1, if k = 1
2(1− [(k − 1)/K(n)]
), otherwise
;
A1,t =1
n− 1
(∑
s 6=t
I(Xm+Lx
t−Lx, Xm+Lx
i,s−Lx, e
) · I(Y
Ly
t−Ly, Y
Ly
s−Ly, e
))− C1
(m + Lx, Ly, e, n
),
A2,t =1
n− 1
(∑
s 6=t
I(XLx
t−Lx, XLx
s−Lx, e
) · I(Y
Ly
t−Ly, Y
Ly
s−Ly, e
))− C2
(Lx, Ly, e, n
),
A3,t =1
n− 1
(∑
s 6=t
I(Xm+Lx
t−Lx, Xm+Lx
s−Lx, e
))− C3
(m + Lx, e, n
),
A4,t =1
n− 1
(∑
s 6=t
I(XLx
t−Lx, XLx
s−Lx, e
))− C4
(Lx, e, n
), and
t, s = max(Lx, Ly
)+ 1, · · · , T −m + 1 .
3 Multivariate Granger Causality Test
In this section, we first discuss the linear Granger causality tests in the multivariate
settings and, thereafter, develop the nonlinear Granger causality test from the bivariate
settings to the multivariate settings.
3.1 Multivariate Linear Granger Causality Test
We first discuss the linear Granger causality test in the multivariate settings.
Linear and Nonlinear Causality Tests 8
3.1.1 Vector Autoregressive Regression
The linear Granger causality test is applied in the vector autoregressive regression (VAR)
scheme. For t = 1, · · · , T , the n-variable VAR model is represented as:
y1t
y2t
...
ynt
=
A10
A20
...
An0
+
A11(L) A12(L) . . . A1n(L)
A21(L) A22(L) . . . A2n(L)...
.... . .
...
An1(L) An2(L) . . . Ann(L)
y1, t−1
y2, t−1
...
yn, t−1
+
e1t
e2t
...
ent
, (3)
where (y1t, · · · , ynt) is the vector of n stationary time series at time t, L is the backward
operator in which Lxt = xt−1, Ai0 are intercept parameters, Aij(L) are polynomials in
the lag operator L such that
Aij(L) = aij(1) + aij(2)L + · · ·+ aij(p)Lp−1
and et = (e1t, · · · , ent)′ is the disturbance vector satisfying the regularity assumption of
the classical linear normal regression model.
In practice, it is common to set all the equations in VAR to possess the same lag length
for each variable. So a uniform order p will be chosen for all the lag polynomials Aij(L) in
the VAR model (3) according to a certain criteria such as Akaike’s information criterion
(AIC) or Schwarz criterion (SC). Along with the Gauss-Markov assumptions satisfied for
the error terms, ordinary least square estimation (OLSE) is appropriate to be used to
estimate the model as it is consistent and efficient. However, long lag length for each
variable will consume large number of degrees of freedom. For example, in the model
stated in equation (3), there will be n(np + 1) coefficients including n intercept terms, n
variances and n(n− 1)/2 covariances to be estimated. When the available sample size T
is not large enough, including too many regressors will make the estimation inefficient,
and thus, cause the test unreliable. To circumvent this problem, one could adopt a Near-
VAR model and seemingly unrelated regressions estimation technique instead of applying
OLSE to estimate the equations simultaneously. We skip the discussion of the Near-VAR
Linear and Nonlinear Causality Tests 9
model and seemingly unrelated regressions estimation in this paper and, for simplicity,
we only use OLSE to estimate the parameters in the VAR model to identify the causality
relationship among vectors of different time series.
3.1.2 Multiple Linear Granger Causality Hypothesis and Likelihood Ratio
Test
To test the linear causality relationship between two vectors of different stationary time
series, xt = (x1,t, · · · , xn1,t)′ and yt = (y1,t, · · · , yn2,t)
′, where there are n1 + n2 = n series
in total, one could construct the following vector autoregressive regression (VAR) model:
xt
yt
=
Ax[n1×1]
Ay[n2×1]
+
Axx(L)[n1×n1] Axy(L)[n1×n2]
Ayx(L)[n2×n1] Ayy(L)[n2×n2]
xt−1
yt−1
+
ext
eyt
, (4)
where Ax[n1×1] and Ay[n2×1] are two vectors of intercept terms, Axx(L)[n1×n1], Axy(L)[n1×n2],
Ayx(L)[n2×n1], and Ayy(L)[n2×n2] are matrices of lag polynomials, ext and eyt are the cor-
responding error terms.
Similar to the bivariate case, there are four different situations for the existence of
linear causality relationships between two vectors of time series xt and yt in (4):
(a) There exists a unidirectional causality from yt to xt if Axy(L) is significantly different
from zero2 and, at the same time, Ayx(L) is not significantly different from zero;
(b) there exists a unidirectional causality from xt to yt if Ayx(L) is significantly different
from zero and, at the same time, Axy(L) is not significantly different from zero;
(c) there exist feedback relations when both Axy(L) and Ayx(L) are significantly different
from zero;
(d) xt and yt are not rejected to be independent when both Axy(L) and Ayx(L) is not
significantly different from zero.
2We said Axy(L) is significantly different from zero if there exists any term in Axy(L) which is signif-icantly different from zero.
Linear and Nonlinear Causality Tests 10
We note that one could consider one more situation as follows:
(e) xt and yt are rejected to be independent when either Axy(L) and Ayx(L) is signif-
icantly different from zero. This is the same situation as either (a), (b) or (c) is
true.
To test the above statements is equivalent to test the following null hypotheses:
(a) H10 : Axy(L) = 0,
(b) H20 : Ayx(L) = 0, and
(c) both H10 and H2
0 : Axy(L) = 0 and Ayx(L) = 0.
One may first obtain the residual covariance matrix Σ from the full model in (4) by
using OLSE for each equation without imposing any restriction on the parameters, and
compute the residual covariance matrix Σ0 from the restricted model in (4) by using OLSE
for each equation with the restriction on the parameters imposed by the null hypothesis,
H10 , H2
0 , or both H10 and H2
0 . Thereafter, besides using the F -test in (1), one could use a
similar approach as in Sims (1980) to obtain the following likelihood ratio statistic:
(T − c)( log|Σ0| − log|Σ| ) (5)
where T is the number of usable observations, c is the number of parameters estimated
in each equation of the unrestricted system, and log|Σ0| and log|Σ| are the natural log-
arithms of the determinants of restricted and unrestricted residual covariance matrices,
respectively. When the null hypothesis is true, this test statistic has an asymptotic χ2
distribution with the degree of freedom equal to the number of restrictions on the coeffi-
cients in the system. For example, when we test H0 : Axy(L) = 0, one should let c equal
to np + 1, and there are n2 × p restrictions on the coefficients in the first n1 equations
of the model. Hence, the corresponding test statistic (T − (np + 1))( log|Σ0| − log|Σ| )
asymptotically follows χ2 with n1 × n2 × p degrees of freedom. The conventional linear
bivariate causality test is a special case of the linear multivariate causality test when
Linear and Nonlinear Causality Tests 11
n1 = n2 = 1. Therefore,besides using the F -test stated in (1), one could also use the
likelihood ratio test in (5) to identify the linear causality relationship for two variables in
the bivariate settings.
3.1.3 ECM-VAR model
Consider (Y1t, · · · , Ynt) to be a vector of n non-stationary time series with cointegration.
Let yit = ∆Yit for i = 1, · · · , n be the corresponding stationary differencing series. In
this situation, one should not use the VAR model as stated in (3), but impose the error-
correction mechanism (ECM) on the VAR to test for Granger causality between these
variables. The ECM-VAR framework is:
y1t
y2t
...
ynt
=
A10
A20
...
An0
+
A11(L) A12(L) . . . A1n(L)
A21(L) A22(L) . . . A2n(L)...
......
An1(L) An2(L) . . . Ann(L)
y1, t−1
y2, t−1
...
yn, t−1
+
α1
α2
...
αn
· ecmt−1 +
e1t
e2t
...
ent
, (6)
where ecmt−1 is the error correction term. In particular, in this paper, we consider to
test the causality relationship between two vectors of non-stationary time series, Xt =
(X1,t, · · · , Xn1,t)′ and Yt = (Y1,t, · · · , Yn2,t)
′, we let xit = ∆Xit and yit = ∆Yit be the
corresponding stationary differencing series, where there are n1 + n2 = n series in total.
If Xt and Yt are cointegrated with residual vector vecmt, then, instead of using the VAR
in (4), one should adopt the following ECM-VAR model:
Linear and Nonlinear Causality Tests 12
xt
yt
=
Ax[n1×1]
Ay[n2×1]
+
Axx(L)[n1×n1] Axy(L)[n1×n2]
Ayx(L)[n2×n1] Ayy(L)[n2×n2]
xt−1
yt−1
+
αx[n1×1]
αy[n2×1]
· ecmt−1 +
ext
eyt
(7)
where Ax[n1×1] and Ay[n2×1] are two vectors of intercept terms, Axx(L)[n1×n1], Axy(L)[n1×n2],
Ayx(L)[n2×n1], Ayy(L)[n2×n2] are matrices of lag polynomials, αx[n1×1] and αy[n2×1] are the
coefficient vectors for the error correction term ecmt−1. Thereafter, one should test the
null hypothesis H0 : Axy(L) = 0 and/or H0 : Ayx(L) = 0 to identify strict causality
relation using the LR test as discussed in Section 3.1.2.
3.2 Multivariate Nonlinear Causality Test
In this section, we will extend the nonlinear causality test for a bivariate setting developed
by Hiemstra and Jones (1994) to a mulitvariate setting.
3.2.1 Multivariate Nonlinear Causality Hypothesis
As discussed in Section 2.2, to identify any nonlinear Granger causality relationship from
any two series, say {xt} and {yt} in a bivariate setting, one has to first apply the linear
models in (1a) and (1b) to {xt} and {yt} to identify their linear causal relationships
and obtain their corresponding residuals, {ε1t} and {ε2t}. Thereafter, one has to apply
a nonlinear Granger causality test to the residual series, {ε1t} and {ε2t}, of the two
variables being examined to identify the remaining nonlinear causal relationships between
their residuals. This is also true if one would like to identify existence of any nonlinear
Granger causality relations between two vectors of time series, say xt = (x1,t, · · · , xn1,t)′
and yt = (y1,t, · · · , yn2,t)′ in a multivariate setting. One has to apply the VAR model in (4)
or the ECM-VAR model in (7) to the series to identify their linear causal relationships and
Linear and Nonlinear Causality Tests 13
obtain their corresponding residuals. Thereafter, one has to apply a nonlinear Granger
causality test to the residual series instead of the original time series. For simplicity, in
this section we will denote Xt = (X1,t, · · · , Xn1,t)′ and Yt = (Y1,t, · · · , Yn2,t)
′ to be the
corresponding residuals of any two vectors of variables being examined.
We first define the lead vector and lag vector of a time series, say Xi,t, similar to the
terms defined in Definition 2.2 as follows. For Xi,t, i = 1, · · · , n1, the mxi-length lead
vector and the Lxi-length lag vector of Xi,t are defined, respectively, as
Xmxii,t ≡ (Xi,t, Xi,t+1, · · · , Xi, t+mxi−1),mxi
= 1, 2, · · · , t = 1, 2, · · · ,
XLxii, t−Lxi
≡ (Xi, t−Lxi, Xi, t−Lxi+1, · · · , Xi, t−1), Lxi
= 1, 2, · · · , t = Lxi+ 1, Lxi
+ 2, · · · .
We denote Mx = (mx1 , · · · ,mxn1), Lx = (Lx1 , · · · , Lxn1
), mx = max(mx1 , · · · ,mxn1),
and lx = max(Lx1 , · · · , Lxn1). The myi
-length lead vector, Ymyii,t , and the Lyi-length lag
vector, YLyii,t−Lyi
, of Yi, t, My, Ly, my, and ly can be defined similarly.
Given mx, my, Lx, Ly, e , we define the following four events:
(a){‖XMx
t −XMxs ‖ < e
} ≡ {‖XMx1i,t −X
mx1i,s ‖ < e, for any i = 1, · · · , n1
};
(b){ ‖ XLx
t−Lx−XLx
s−Lx‖< e
} ≡ {‖XLxii,t−Lxi
−XLxii,s−Lxi
‖ < e, for any i = 1, · · · , n1
};
(c){‖Y My
t − YMys ‖ < e
} ≡ {‖Y myii,t − Y
myii,s ‖ < e, for any i = 1, · · · , n2
}; and
(d){ ‖ Y
Ly
t−Ly− Y
Ly
s−Ly‖< e
} ≡ {‖Y Lyii,t−Lyi
− YLyii,s−Lyi
‖ < e, for any i = 1, · · · , n2
},
where ‖ · ‖ denotes the maximum norm defined in Definition 2.2.
The vector series {Yt} is said not to strictly Granger cause another vector series {Xt}if:
Pr(‖XMx
t −XMxs ‖ < e
∣∣ ‖ XLxt−Lx
−XLxs−Lx
‖< e, ‖ YLy
t−Ly− Y
Ly
s−Ly‖< e,
)
= Pr(‖XMx
t −XMxs ‖ < e,
∣∣ ‖ XLxt−Lx
−XLxs−Lx
‖< e)
,
Linear and Nonlinear Causality Tests 14
where Pr(· | · ) denotes conditional probability.
3.2.2 Test Statistic and It’s Asymptotic Distribution
Similar to the bivariate case, the test statistic for testing non-existence of nonlinear
Granger causality can be obtained as follows:
√n
(C1
(Mx + Lx, Ly, e, n
)
C2
(Lx, Ly, e, n
) − C3
(Mx + Lx, e, n
)
C4
(Lx, e, n
))
(8)
where
C1
(Mx + Lx, Ly, e, n
) ≡ 2
n(n− 1)
∑∑t<s
n1∏i=1
I(x
mxi+Lxii,t−Lxi
, xmxi+Lxii,s−Lx
, e) ·
n2∏i=1
I(y
Lyii,t−Lyi
, yLyii,s−Lyi
, e) ,
C2
(Lx, Ly, e, n
) ≡ 2
n(n− 1)
∑∑t<s
n1∏i=1
I(x
Lxii,t−Lxi
, xLxii,s−Lx
, e) ·
n2∏i=1
I(y
Lyii,t−Lyi
, yLyii,s−Ly
, e),
C3
(Mx + Lx, e, n
) ≡ 2
n(n− 1)
∑∑t<s
n1∏i=1
I(x
mxi+Lxii,t−Lx
, xmxi+Lxii,s−Lxi
, e),
C4
(Lx, e, n
) ≡ 2
n(n− 1)
∑∑t<s
n1∏i=1
I(x
Lxii,t−Lxi
, xLxii,s−Lxi
, e), and
t, s = max(Lx, Ly
)+ 1, · · · , T −mx + 1, n = T + 1−mx −max
(Lx, Ly
).
Theorem 3.1. To test the null hypothesis, H0, that {Y1,t, · · · , Yn2,t} does not strictly
Granger cause {X1,t, · · · , Xn1,t}, under the assumptions that the time series {X1,t, · · · , Xn1,t}and {Y1,t, · · · , Yn2,t} are strictly stationary, weakly dependent, and satisfy the mixing con-
ditions stated in Denker and Keller(1983), if the null hypothesis, H0, is true, the test
statistic defined in (8) is distributed as N(0, σ2(Mx, Lx, Ly, e)
). When the test statistic
in (8) is too far away from zero, we reject the null hypothesis. A consistent estimator of
σ2(Mx, Lx, Ly, e) follows:
σ2(Mx, Lx, Ly, e) = ∇f(θ)T · Σ · ∇f(θ)
Linear and Nonlinear Causality Tests 15
in which each component Σi,j (i, j = 1, · · · , 4), of the covariance matrix Σ is given by:
Σi,j = 4 ·∑
k≥1
ωkE(Ai,t · Aj,t+k−1),
ωk =
1 if k = 1
2, otherwise,
A1,t = h11
(xMx+Lx
t−Lx, y
Ly
t−Ly, e
)− C1(Mx + Lx, Ly, e) ,
A2,t = h12
(xLx
t−Lx, y
Ly
t−Ly, e
)− C2(Lx, Ly, e) ,
A3,t = h13
(xMx+Lx
t−Lx, e
)− C3(Mx + Lx, e) , and
A4,t = h14
(xLx
t−Lx, e
)− C4(Lx, e) ,
where h1i(zt), i = 1, · · · , 4, is the conditional expectation of hi(zt, zs) given the value of
zt as follows:
h11
(xMx+Lx
t−Lx, y
Ly
t−Ly, e
)= E
(h1
∣∣ xMx+Lxt−Lx
, yLy
t−Ly
),
h12
(xLx
t−Lx, y
Ly
t−Ly, e
)= E
(h2
∣∣ xLxt−Lx
, yLy
t−Ly
),
h13
(xMx+Lx
t−Lx, e
)= E
(h3
∣∣ xMx+Lxt−Lx
), and
h14
(xLx
t−Lx, e
)= E
(h4
∣∣ xLxt−Lx
).
A consistent estimator of Σi,j elements is given by:
Σi,j = 4 ·K(n)∑
k=1
ωk(n)
[1
2(n− k + 1)
∑t
(Ai,t(n) · Aj,t−k+1(n) + Ai,t−k+1(n) · Aj,t(n)
)],
K(n) = [n1/4] , ωk(n) =
1 if k = 1
2(1− [(k − 1)/K(n)]) otherwise,
Linear and Nonlinear Causality Tests 16
A1,t =1
n− 1
(∑
s 6=t
n1∏i=1
I(X
mxi+Lxii,t−Lxi
, Xmxi+Lxii,s−Lx
, e) ·
n2∏i=1
I(Y
Lyii,t−Lyi
, YLyii,s−Lyi
, e))
− C1
(Mx + Lx, Ly, e, n
),
A2,t =1
n− 1
(∑
s 6=t
n1∏i=1
I(X
Lxii,t−Lxi
, XLxii,s−Lx
, e) ·
n2∏i=1
I(Y
Lyii,t−Lyi
, YLyii,s−Ly
, e))
− C2
(Lx, Ly, e, n
),
A3,t =1
n− 1
(∑
s 6=t
n1∏i=1
I(X
mxi+Lxii,t−Lx
, Xmxi+Lxii,s−Lxi
, e))− C3
(m + Lx, e, n
),
A4,t =1
n− 1
(∑
s 6=t
n1∏i=1
I(X
Lxii,t−Lxi
, XLxii,s−Lxi
, e))− C4
(Lx, e, n
),
t, s = max(Lx, Ly
), · · · , n and n = T −mx −max(Lx + Ly) + 1 ,
and a consistent estimator of ∇f(θ) is:
∇f(θ) =
[1
θ2
, − θ1
θ22
, − 1
θ4
,θ3
θ24
]T
=
[1
C2
(Lx, Ly, e, n
) , −C1
(m + Lx, Ly, e, n
)
C22
(Lx, Ly, e, n
) , − 1
C4
(Lx, e, n
) ,C3
(Mx + Lx, e, n
)
C24
(Lx, e, n
)]T
.
4 Monte Carlo Simulation
In this section, we present the Monte Carlo simulation3 to demonstrate the superiority of
our proposed multivariate nonlinear Granger causality test over its bivariate counterpart
in the performance of both size and power when the underlying series possess multivariate
nonlinear Granger causality nature.
We have conducted simulations for a variety of time series possessing different multi-
variate nonlinear Granger causality relationships. All simulations show that our proposed
3Readers may refer to Tiku et al (1998, 1999a, 1999b, 2000) and Lean et al (2008) for more informationon simulation.
Linear and Nonlinear Causality Tests 17
multivariate nonlinear Granger causality test performs better in both size and power. For
simplicity, we only present the results of the following equation:
Xt = β Yt−1Zt−1 + εt (9)
where {Yt} and {Zt} are i.i.d. and mutually independent random variables generated from
N(0, 1), {εt} is Gaussian white noise generated from N(0, 0.1). Under the model in (9),
the variables {Yt, Zt} nonlinear Granger cause {Xt} if β 6= 0 and there is no Granger
causality relationship if β = 0. The bivariate nonlinear Granger causality test could
detect the bivariate causality relationships well but it may not be able to examine the
causality relationships under multivariate settings including the one set in (9). Thus,
we expect that our proposed multivariate test could perform better than its bivariate
counterpart in this model setting. To justify our claim, we conduct a simulation with
1,000 Monte Carlo runs based on sample size of 50 and 100 observations for each β value.
We set lead length m = 1 and the common lag length Lx = Ly = Lz for all the cases
being examined. A common scale parameter of e = 1.5σ is used where σ = 1 denotes the
standard deviation of standardized series. In the simulation of each replication, the values
of the test statistics for different common lag lengths are compared with their asymptotic
critical values at the 0.05 nominal significance level. The percentage of rejecting the null
of β = 0 is reported in Tables 1 and 2 for sample size of 50 and 100, respectively.
Table 1 displays the simulation results of sample size 50 with the value of β varying
from −0.5 to 0.5 and the common lag length being 1, 2, and 3 for all the cases under
examination. When β = 0, that is, {Xt} is “independent” with both {Yt} and {Zt} imply-
ing that the null hypothesis is true, both bivariate and multivariate tests are conservative
when the common lag length = 1, 2. When the common lag length is equal to 3, both
tests have empirical sizes similar to the nominated significance level of 0.05. In short,
Table 1 exhibits that (a) the average of the simulated size of multivariate test is closer to
the nominated significance level of 0.05. When β is nonzero, our simulation shows that
(b) the powers of both bivariate and multivariate tests perform better when lag length =
Linear and Nonlinear Causality Tests 18
1 and their powers reduce when lag length increases, and (c) the power of our proposed
multivariate test is much higher than that of its bivariate counterpart for any lag length
being examined in our paper. We note that (b) is reasonable because only lag one of
both Y and Z “cause” X in (9) while our findings in (a) and (c) show that our proposed
multivariate test performs better than its bivariate counterpart in both size and power.
We turn to examine both size and power when we increase the sample size to 100.
The results are displayed in Table 2. As the sample size is larger, we report results with
longer lag length scale including Lx = Ly = Lz = 1, 3, and 5.4 Comparing with sample
size = 50, the simulation results show that our observations of (a), (b), and (c) for sample
size = 50 still hold for sample size of 100, but, as expected, both size and power for both
bivariate and multivariate tests have improved and our findings are consistent to show
that our proposed multivariate test performs better than its bivariate counterpart in both
size and power when sample size = 100.
Table 1: Size and power comparison between bivariate and multivariate nonlinear Grangercausality tests when sample size=50
Beta -0.5 -0.4 -0.3 -0.2 -0.1 -0.05 0 0.05 0.1 0.2 0.3 0.4 0.5Lags=1Bivariate 0.917 0.875 0.833 0.775 0.413 0.114 0.016 0.129 0.384 0.748 0.851 0.894 0.902
Multivariate 0.996 1.000 0.997 0.987 0.716 0.204 0.029 0.220 0.686 0.981 1.000 0.999 0.999Lags=2Bivariate 0.645 0.655 0.624 0.516 0.240 0.100 0.034 0.126 0.255 0.509 0.598 0.647 0.644
Multivariate 0.983 0.979 0.956 0.870 0.427 0.144 0.032 0.165 0.468 0.881 0.956 0.979 0.982Lags=3Bivariate 0.465 0.452 0.444 0.333 0.178 0.072 0.049 0.073 0.162 0.355 0.422 0.460 0.433
Multivariate 0.864 0.850 0.796 0.676 0.293 0.115 0.045 0.106 0.310 0.655 0.789 0.842 0.853
Bivariate 0.676 0.661 0.634 0.541 0.277 0.095 0.033 0.109 0.267 0.537 0.624 0.667 0.660Multivariate 0.948 0.943 0.916 0.844 0.479 0.154 0.035 0.164 0.488 0.839 0.915 0.940 0.945
Note: The last two rows display the average values for the case of “Bivariate” and “Multivariate”,respectively, for the corresponding value of β.
4We have examined other lag lengths and the results are consistent with our findings. Thus, we skipreporting other lag lengths to save space.
Linear and Nonlinear Causality Tests 19
Table 2: Size and power comparison between bivariate and multivariate nonlinear Grangercausality tests when sample size=100
Beta -0.5 -0.4 -0.3 -0.2 -0.1 -0.05 0 0.05 0.1 0.2 0.3 0.4 0.5Lags=1Bivariate 1.000 1.000 0.996 0.989 0.781 0.266 0.029 0.271 0.807 0.994 0.999 0.997 0.999
Multivariate 1.000 1.000 1.000 1.000 0.971 0.448 0.037 0.452 0.977 1.000 1.000 1.000 1.000Lags=3Bivariate 0.872 0.842 0.823 0.740 0.394 0.122 0.046 0.107 0.406 0.700 0.812 0.836 0.846
Multivariate 1.000 0.999 0.993 0.973 0.636 0.145 0.048 0.169 0.604 0.963 0.990 0.997 1.000Lags=5Bivariate 0.561 0.554 0.508 0.453 0.189 0.075 0.048 0.072 0.210 0.412 0.525 0.577 0.532
Multivariate 0.865 0.823 0.776 0.676 0.256 0.105 0.049 0.104 0.264 0.645 0.788 0.842 0.870
Bivariate 0.811 0.799 0.776 0.727 0.455 0.154 0.041 0.150 0.474 0.702 0.779 0.803 0.792Multivariate 0.955 0.941 0.923 0.883 0.621 0.233 0.045 0.242 0.615 0.869 0.926 0.946 0.957
Note: The last two rows display the average values for the case of “Bivariate” and “Multivariate”,respectively, for the corresponding value of β.
5 Illustration
Qiao, et al (2008) examine the bivariate linear and nonlinear Granger causality rela-
tionships between pairs of daily returns from five indices: (a) Shanghai A shares (SHA)
and Shanghai B shares (SHB) from Shanghai Stock Exchange (SHSE), (b) Shenzhen A
shares (SZA) and Shenzhen B shares (SZB) from Shenzhen Stock Exchange (SZSE), and
(c) Hong Kong H shares (H) before and after February 19, 2001, the date the Chinese
Government allowed domestic citizens to trade B shares from this date onwards5.
As they only apply the bivariate Granger causality test to study the issue, their results
may not be able to capture the multivariate causality relationships among these indices.
To bridge the gap, in this paper we first apply the traditional multivariate linear Granger
causality test and thereafter apply our proposed multivariate nonlinear causality test
to examine the existence of multivariate linear and nonlinear causality relationships in
any of the following three groups for the segmented Chinese stock markets before and
after February 19, 2001: (a) A-share (including SHA and SZA) and B-share (including
SHB and SZB), (b) Shanghai stock market (including SHA and SHB) and Shenzhen
stock market(including SZA and SZB), and (c) domestic stock market (A-share) and
5Readers may refer to Qiao, et al (2008) for detailed information on SHA, SZA, SHB, SZB, and H.
Linear and Nonlinear Causality Tests 20
foreigner-invested stock market (including B-share and H-share). The studying period
is from October 6, 1992 to December 31, 2007 and all data are taken from DataStream
International. For easy comparison, we follow Qiao, et al (2008) to use February 19, 2001
as the cut-off point so that the first sub-period is from October 6, 1992 to February 16,
2001 and the second sub-period is from February 19, 2001 to December 31, 2007.
We first adopt the VAR model in (4) or the ECM-VAR model in (7) to examine whether
there is any multivariate linear Granger causality relationship among the indices in any
of the groups mentioned above. We find that, in the first subperiod, there is only strong
unidirectional linear causality from Shenzhen stock market to Shanghai stock market.
On the other hand, in the second sub-period, we find that (a) there is unidirectional
linear causality from B-share to A-share, and (b) there are strong feedback causality
relationships between Shanghai stock market and Shenzhen stock market, and between
domestic stock market and foreigner-invested stock market6.
After checking the multivariate linear causalities, we apply our new proposed multi-
variate nonlinear Granger causality test to the error terms from the estimated VAR or
ECM-VAR models to investigate whether there is any remaining undetected multivariate
nonlinear relationship among the indices. We set the common lead length m = 1 and
the common lag length to be 1 to 10. A common scale parameter of e = 1.5σ is used,
where σ = 1 denotes the standard deviation of standardized series. The values of the
standardized test statistic of (8) are reported in Table 3. Under the null hypothesis of no
multivariate nonlinear Granger causality, the test statistic is asymptotically distributed as
N(0, 1). Therefore, very large or small values of the test statistic lead to the rejection of
null hypothesis, or equivalently, indicate the existence of multivariate nonlinear causality.
The results show that, in the first subperiod, (a) there is weak nonlinear causality
from B-share to A-share, and (b) there is strong bi-directional nonlinear causality between
Shenzhen and Shanghai stock markets, since the test statistics of SZ→SH are significant
6The detailed results of the multivariate linear causality test are available upon request.
Linear and Nonlinear Causality Tests 21
at the 0.05 level for all lags, and the test statistics of SH→SZ are significant at the 0.05
level for the first half of lags. In the second sub-period, our results infer that (c) there
exists strong feedback nonlinear causality between Shenzhen and Shanghai stock markets
similar to the results of the first subperiod, (d) there is strong unidirectional nonlinear
causality from A-share to B-share, since the test statistics of A→B are significant at
the 0.05 level for some lags, and (e) there exists weak nonlinear causality from domestic
stock market to foreigner-invested stock market, as there are two test statistics to be
significant. Our findings infer that there are more nonlinear causality among the indices
after the Chinese Government introduced the policy on February 19, 2001.
6 Conclusion Remarks
In this paper, we first discuss linear causality tests in multivariate settings and thereafter
develop a nonlinear causality test in multivariate settings.
However, there is a disadvantage of the Hiemstra-Jones test. For example, Diks and
Panchenko (2005) point out that Hiemstra-Jones test might have an over-rejection bias
on the null hypothesis of Granger non-causality. Their simulation results show that rejec-
tion probability will goes to one as the sample size increases. Diks and Panchenko (2006)
address this problem by replacing the global test by an average of local conditional depen-
dence measures. Their new test shows weaker evidence for volume causing returns than
Hiemstra-Jones test does. Besides Hiemstra-Jones test, other forms of nonlinear causality
test has also been developed. For example, Marinazzo, Pellicoro, and Stramaglia (2008)
adopt theory of reproducing kernel Hilber spaces to develop nonlinear Granger causal-
ity test. And Diks and DeGoede (2001) develop an information theoretic test statistics
for Granger causality. They use bootstrap methods instead of asymptotic distribution
to calculate the significance of the test statistics. Thus, further extension of this paper
could include to develop multivariate settings for the more powerful linear and nonlinear
causality tests.
Linear and Nonlinear Causality Tests 22
Table 3: Multiple Nonlinear Testing Results for China’s Stock Markets
First Sub-Period Second Sub-Periodlags B→A SZ→SH B,H→A B→A SZ→SH B,H→A1 1.620* 4.499*** 0.617 0.358 1.434* 1.2142 1.413* 4.882*** 0.344 0.947 3.361*** 1.0193 0.512 4.610*** -0.591 0.376 4.085*** 0.6094 0.546 4.179*** -0.418 -0.541 3.638*** -0.1785 -0.187 3.971*** -0.800 -1.217 3.359*** -1.3056 -0.704 3.523*** -1.024 -1.018 3.031*** -1.1587 -1.663 2.953*** -1.465 -0.961 2.846*** -0.6258 -1.858 2.863*** -1.249 -1.191 1.990** -0.8799 -1.859 2.375*** -1.058 -1.331 2.084** -1.42610 -2.186 1.887** -1.054 -1.283 1.733** -0.778
lags A→B SH→SZ A→B,H A→B SH→SZ A→B,H1 -2.130 3.071*** -1.638 2.098** 2.611*** 2.309**2 -2.423 2.983*** -1.171 2.311** 2.792*** 2.708***3 -2.052 1.896** -1.049 2.282** 2.599*** 1.2324 -1.901 2.381*** -1.263 1.673** 1.827** 0.2245 -1.104 1.754** -1.428 1.115 1.474* -0.6006 -1.201 1.505* -1.461 1.649** 1.308* -1.1287 -1.325 1.091 -0.943 1.569* 0.907 -0.7668 -0.961 0.793 -1.204 1.329* 0.933 -0.9439 -1.177 0.843 -1.165 1.122 0.726 -0.77410 -1.371 0.294 -0.636 1.222 0.913 -0.597
Note: ***, **, and * represent significance levels of 1%, 5%, and 10%, respectively. A includesSHA and SZA, B includes SHB and SZB, SH includes SHA and SHB, and SZ includes SZAand SZB. The first sub-period is from October 6, 1992 to February 16, 2001 while the secondsub-period is from February 19, 2001 to December 31, 2007.
Linear and Nonlinear Causality Tests 23
At last, we note that linear and nonlinear causality tests could be used in medical
sciences, physical sciences, social sciences, and many other areas, especially in finance and
economics. The tests could be used to examine many important economics and financial
issues, see, for example, Fong et al (2005, 2008) and Broll et al (2006), and to explain
many financial anomalies, see, for example, Manzur et al (1999), Wan and Wong (2001),
and Lam et al (2010). The results drawn from the linear and nonlinear causality tests
could assist investors in their decision making of their investment. In order to obtain
better information in their decision making, investors may consider to incorporate the
findings from linear and nonlinear causality tests with other techniques7 to obtain better
investment decision making.
7For example, portfolio optimization (Leung and Wong, 2008, Bai et al., 2009a,b; Egozcue and Wong,2010), technical analysis (Wong et al; 2001, 2003; Kung and Wong, 2009), fundamental analysis (Thomp-son and Wong, 1991, 1006; Wong and Chan, 2004), and stochastic dominance theory, see, for example,Wong (2007), Wong and Chan (2008), Wong and Ma (2008), Sriboonchita et al (2009) and the referencestherein for more information.
Linear and Nonlinear Causality Tests 24
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IT Stock Market Dominate Other IT Stock Markets: Evidence from Multivariate
GARCH Model, Economics Bulletin, 6(27), 1-7.
Linear and Nonlinear Causality Tests 27
[28] Qiao, Z., M. McAleer, W.K. Wong, (2009), Linear and Nonlinear Causality of Con-
sumption Growth and Consumer Attitudes, Economics Letters 102(3), 161-164.
[29] Serfling, R., (1980), Approximation Theorems of Mathematical Statistics John Wiley
& Sons, New York.
[30] Sims, Chirstopher A. (1980), Macroeconomics and Reality, Econometrica 48, 1-48.
[31] Songsak Sriboonchita, Wing-Keung Wong, Sompong Dhompongsa, Hung T. Nguyen,
(2009), Stochastic Dominance and Applications to Finance, Risk and Economics,
Chapman and Hall/CRC, Taylor and Francis Group, Boca Raton, Florida, USA.
[32] Thompson, H.E. and W.K. Wong, (1991), On the Unavoidability of ‘Unscientific’
Judgment in Estimating the Cost of Capital, Managerial and Decision Economics,
12, 27-42.
[33] Thompson, H.E. and W.K. Wong, (1996), Revisiting ’Dividend Yield Plus Growth’
and Its Applicability, Engineering Economist, Winter, 41(2), 123-147.
[34] Tiku, M.L. and W.K. Wong, (1998), Testing for unit root in AR(1) model using
three and four moment approximations, Communications in Statistics: Simulation
and Computation, 27(1), 185-198.
[35] Tiku, M.L., W.K. Wong, and G. Bian, (1999a), Time series models with asymmetric
innovations, Communications in Statistics: Theory and Methods, 28(6), 1331-1360.
[36] Tiku, M.L., W.K. Wong, and G. Bian, (1999b), Estimating Parameters in Autore-
gressive Models in Non-normal Situations: symmetric Innovations, Communications
in Statistics: Theory and Methods, 28(2), 315-341.
[37] Tiku, M.L., W.K. Wong, D.C. Vaughan, and G. Bian, (2000), Time series models
in non-normal situations: Symmetric innovations, Journal of Time Series Analysis,
21(5), 571-596.
Linear and Nonlinear Causality Tests 28
[38] Wan, Henry Jr and W.K. Wong, (2001), Contagion or Inductance: Crisis 1997 Re-
considered, Japanese Economic Review, 52(4), 372-380.
[39] Wong, Wing Keung, (2007), Stochastic dominance and mean-variance measures of
profit and loss for business planning and investment, European Journal of Opera-
tional Research, 182, 829-843.
[40] Wong, Wing-Keung and Raymond Chan, (2004), On the estimation of cost of capital
and its reliability, Quantitative Finance, 4(3), 365 - 372.
[41] Wong, Wing-Keung and Raymond Chan, (2008), Markowitz and Prospect Stochastic
Dominances, Annals of Finance 4(1), 105-129.
[42] Wong W.K., B.K. Chew and D. Sikorski (2001), Can P/E ratio and bond yield be
used to beat stock markets? Multinational Finance Journal, 5(1), 59-86.
[43] Wong, Wing-Keung, Habibullah Khan and Jun Du, (2006), Money, Interest Rate,
and Stock Prices: New Evidence from Singapore and USA, Singapore Economic
Review, 51(1), 31-52.
[44] Wong, Wing-Keung and Chenghu Ma, (2008), Preferences over Location-Scale Fam-
ily, Economic Theory 37(1), 119-146.
[45] Wong W K, M. Manzur, and B.K. Chew (2003), How Rewarding is Technical Anal-
ysis? Evidence from Singapore Stock Market, Applied Financial Economics, 13(7),
543-551.