1. Introduction
Rapid exchange of information and investment between different economies promote zonal logistics and transportation. The development of Transportation can meet the needs of the economy and enables the circulation of goods in different zones, which can stimulate the improvement of the zonal economy and enhance the attraction of the zonal economy. Accordingly, rapid economic growth produces large transport demands and results in the motivation to promote transportation. The mechanism between transportation and economic growth provides the basis for formulating the development strategy for the zonal economy and transportation, which can promote the coordination of zonal economic and transport development. Studies on the correlation between transportation and economic improvement are conducive to understand the factors that influence the advancement of a zone on the whole.
A large amount of literature has investigated the correlation between transportation and economic development [
1,
2]. However, whether the development of transportation promotes economic development or vice versa is still a matter of debate. A number of studies suggested transportation system development has a positive impact on economic growth [
3,
4]. Other studies have shown that economic growth may have a positive feedback effect on transportation [
5]. Numerous empirical studies have identified a long-run equilibrium relationship between transportation and economic development [
6]. Some studies have found a bidirectional relationship between transportation infrastructure and economic growth [
4,
7]. The previous studies cannot determine whether the relationship between transportation and economic development is one-way or interactive. The interrelationship between them remains unclear. It is necessary to further analyze the relationship of causality direction between transportation and economic development. In addition, only a few studies have attempted to identify the interaction between China’s transportation and zonal economic growth, and no clear consensus has been reached in the literature regarding this interaction.
The circulation of goods is an essential indicator of the development of transportation. In the transportation system, zonal freight turnover closely relates to economic development. The gross domestic product (GDP) is the index that can best evaluate the economic development of a country or zone. Several studies have analyzed the bidirectional relationship between freight transportation using various approaches. However, these approaches have limitations. First, most methods do not make it easy to determine endogenous and exogenous variables since the variables about social and economic are generally interdependent. Second, several approaches such as structural equation modeling (SEM) cannot consider the dynamic relationship. The lagged effects cannot be incorporated into the model. Third, several models focus on the sensitivity analysis of the variables but are difficult to be used in forecasting and simulation.
Therefore, the purpose of this paper is to analyze the relationship of causality direction between freight and economic growth using the econometric method to provide decision support for public policies for transportation and economic development. The VAR and VECM were used to analyze the relationship between freight turnover and GDP of different zones in this paper. In the VAR and VECM, all of the variables are endogenous. Besides, the lags of all variables can be considered in the model. Moreover, the lagged rank of the model can be calibrated by test. The results of the model can be used in forecasting or simulation simply and intuitively. China appears to have obvious progress in economic and transportation infrastructure in the past decades due to the development stages. Besides, China’s various policies have promoted infrastructure development and economic growth in different zones. Economic growth and transport data in china may be easy to observe and compare. Therefore, GDP and freight turnover data collected in China at the zonal level were used to estimate the VAR model. Moreover, the development status of each zone was evaluated. This study provides suggestions on the development of zonal transportation and logistics based on the relationship between economics and transportation, which can provide a basis for different zones to adopt relevant policies and measures.
The hypothesis is that transportation has a positive impact on zonal economic growth, while we hypothesize transportation and regional economic growth have a causal relationship for Chinese zones. To test our hypothesis, the VAR and VECM are applied to determine the relationship between GDP and freight turnover for economic zones of stationary series and non-stationary sequences. In addition, the Granger causality analysis is used to examine the causality direction between freight transportation and economic using zonal data.
The contribution of this study is reflected in three aspects. First, this study analyzes the relationship of causality direction between freight transportation and economic growth considering the lag effect. The interrelationship between them remains unclear. Second, previous studies do not obviously consider heterogeneity in determining the interaction between transportation and zonal economy in China. There are more economic activities in the eastern coastal zones, while economic development in other zones is relatively lagged. In addition, there are large differences in the level of transportation system development between zones. The relationship between transportation and economic growth ignoring spatial heterogeneity could cause partial estimation results, hence leading to a misleading inference about causal relationships [
8]. Therefore, integrating potential differences in the relationship between transportation and economic growth across zones in our study offers reliable information for the government to coordinate the zonal development and reduce the zonal gap. Third, this study could benefit the China government from more valuable decisions for transportation investment at the zonal level by understanding the relationship between transportation and economy by zone. By doing so, the sustainable development of the economy and society can be realized through reasonable investment and resource allocation of transportation.
This paper first reviews the literature on the relationship between the transportation system and the economy.
Section 3 analyzes the data and describes the methods.
Section 4 gives the results, followed by a detailed discussion of the possible policy effects.
Figure 1 presents the main research ideas.
3. Data and Methodology
The data of freight turnover and GDP were obtained from the national bureau of statistics in China [
40]. The data show that the freight turnover of national transportation increased from 49,718 million ton
km in 2003 to 199035 million ton
km in 2018, an increase of about 3 times. In 2018, China’s GDP was 914707 billion yuan, up to 5.7 times from 136,576 billion yuan in 2003.
Figure 2 shows a map showing the location of the zones described in
Table 1.
The economic zones of China are divided into seven according to the division method of the China state council and considering the GDP data and growth trend of each province.
Table 1 shows the specific division results and the value of GDP and freight turnover of each economic zone.
First, the traffic and economic characteristics of each economic zone are analyzed, and then the stationarity test is carried out for GDP and freight turnover. If it is stable, the VAR model can be established; if it is not stable, co-integration analysis can be carried out. If there is a co-integration relationship between GDP and freight turnover, the VECM model can be established. Finally, the Granger causality test is used to understand the relationship of causality direction between transportation and economic development for different zones. The method is shown below.
3.1. The Characteristic of the Research Area
Before using the data from 2003 to 2018, the correlation test should be conducted on the freight situation and the GDP in each zone of the whole country to eliminate the sequences that do not meet the requirements. Pearson correlation coefficient method is adopted in this study to test the correlation between zonal freight turnover and GDP.
Table 2 shows the results.
Table 2 shows that except for the low correlation between the GDP and the freight turnover of the Circum Bohai-Sea economic zone, a strong correlation exists between the freight turnover and GDP of each economic zone.
A possible interpretation of this result would be that the freight turnover does not always increase with the construction of transportation facilities due to a lack of efficient utilization of them. Moreover, other conditions such as the government’s policy environment, management, and control system might cause a difference in economic growth.
3.2. Test for Stationary
The unit root test is adopted to the test stationary of the sequence. It is conducted firstly to avoid pseudo regression caused by OLS. The augmented Dickey–Fuller test [
41] is known for testing the stability of the variables and tests the following equation:
where
yt is the time series to be tested,
xt are optional exogenous repressors, which may contain a constant;
a and
b are parameters to be estimated,
εt are white noise error terms,
m is the maximum lag length and
D is the difference operator.
Null hypothesis
H0:
d = 0 is tested against the alternative
Ha:
d < 0. If the null hypothesis is true, then the unit root is present, and the series is non-stationary. When the null hypothesis is rejected, the series is stationary. The critical values for the test statistic are given by MacKinnon [
30].
If the sequence is stationary, the VAR model can be established. VAR modeling has a lag interval for time, in which the lag time is optimal and unknown. Therefore, we need to try to select different lag periods. AIC and SC are commonly used to compare the models. The model with the smallest Akaike Information Criterion (AIC) or Schwarz Criterion (SC) was selected so that the VAR model can be reliable. The AIC and AC can be obtained by the following formula
In the VAR model (4),
is the total number of estimated parameters,
k is the number of endogenous variables,
T is the sample length,
d is the number of exogenous variables,
p is the lag order and
l is determined by the following formula.
represents the estimation of the residual covariance matrix of the VAR model.
The basic mathematical expression of the VAR model is written as formula (5).
where
is
K dimensional endogenous variable vector;
is
D dimensional exogenous variable vectors;
p is lag order;
t is the number of the sample;
A is
k by
d matrix;
B is estimated coefficient matrix;
is
K dimensional perturbation vector.
These variables can be correlated from one another synchronously, but not with their lag value. Besides, the variables on the right-hand side of the equation, assuming that
is the covariance matrix, are a
k by
k positive definite matrix. Formula (5) can be expressed as a matrix.
That is, the VAR model with k time series variables is composed of k equations.
3.3. Co-Integration Analysis
If the unit root test of a sequence is not stationary, co-integration analysis is performed after the first-order difference. Co-integration between variables stand for a long-run equilibrium relationship. If the variables are non-stationary and are integrals of the same order, then I (1) is called, but their linear combination is stationary, that is I (0). The Johansen test of co-integration approach tests is presented as follows:
where
is a vector of
k non-stationary I(1) variables,
is a vector of deterministic variables,
and
are parameters to be estimated,
is a vector of innovations and
p is the order of VAR.
A VECM can be established if a co-integration relationship exists between sequences.
where
is the error correction term,
is the adjustment factor,
is residual error sequence, and
and
are the coefficients.
In the explained variables in the short term, the change is relatively stable. In the long-term trend and short-term swings in the short term, the size of the system from the degree of equilibrium directly leads to the size of the wave amplitude. In the long run, a co-integration relationship has the effect of the gravity line and the unbalanced state back to equilibrium.
3.4. Granger Causality
Granger causality test is used to understand the relationship of causality direction between transportation and economic development in each economic zone. The Granger causality analysis tests whether it is possible to incorporate the lagged variables into the equations of other variables. A variable is considered to have Granger causality if the variable is affected by the hysteresis of other variables. In a binary
p-order VAR model:
Only if all coefficients
in the coefficient matrix are 0, then the variable cannot cause
y by Granger, which is equivalent to the notion that the variable
x is exited from the variable
y. At this point, the direct method to determine the cause of Granger is to use the
F test to test the following joint test:
: At least one q exists so that .
Its statistic is as follows:
Equation (10) follows an
F distribution. If
S is greater than the critical value, the null hypothesis is rejected. Others support the null hypothesis:
x cannot cause
y by Granger, where RSS is the sum of squared residuals of
y equation in Equation (6).
is a lagging variable without
x (
,
q = 1,2, …,
p), such as the sum of the squared residuals of the following equation:
Under the assumption that the Gaussian distribution is satisfied, the test statistic Equation (10) has an accurate
F distribution. If the regression
t-shaped form is the VAR model of Equation (9), then an asymptotic equivalence test can be given by the following formula:
If S2 is greater than the threshold value of x, then the null hypothesis is rejected. Otherwise, the null hypothesis that x cannot be caused by Granger is accepted.
5. Discussion and Policy Implications
This study investigates the dynamic and bidirectional correlation between freight volume and economic development considering the lagged effects, using the data of freight turnover and GDP from 31 provinces in China. VAR model is exploited to build the relationship between GDP and freight turnover in economic zones of stationary series, whereas VECM is established in the Northeast economic zone, which is proved to have a co-integration relationship. The impulse response analysis and variance decomposition are conducted to verify the effectiveness of the model. In addition, the Granger causality test is conducted. The main findings and discussions are as follows.
(1) The relationship between freight turnover and GDP in the Northeast economic zone is bidirectional. This result is consistent with several previous studies that found the interactive impact of transportation and economic growth. Meng et al. [
21] found that the relationship between railway transportation and economic improvement was mutually promoting. This same finding is also supported by Pradhan et al. [
7], which suggested that transportation infrastructure promoted economic growth and, economic growth had also boosted transport infrastructure in return.
(2) A unidirectional relationship exists between freight turnover and GDP in the Circum Bohai-Sea, the Pearl River, Middle Part, Southwest, and Northwest economic zone. The unidirectional relationship between freight transportation and GDP found in our analysis is consistent with Saidi et al. [
9] who suggested that transportation contributes to economic growth. Moreover, our result is in line with several previous studies that found a significant impact of road infrastructure on economic growth [
10,
12].
(3) However, the Granger causality is not obvious in the Yangtze River economic zone. A plausible interpretation of this result would be that it is insufficient to create growth by merely enhancing accessibility. The freight turnover does not always increase with the construction of transportation facilities due to a lack of efficient utilization of them. Moreover, other conditions such as the political situation, management, and control system might cause a difference in economic growth. This result is supported by Park et al. [
20], who examined the role of various types of transport infrastructure in economic growth. Results showed that air and land transport in developing countries were often independent of economic growth.
The results show that the relationship of causality direction between economy and freight transportation is not the same in each economic zone. The lack of a consistent pattern of causality suggests that there are many other factors influencing causality at the zonal level between GDP and freight turnover in the real world. For example, there is trade into and out of the economic zones. The closer the economic zone and the quality of the transport infrastructure, the more likely it would be that there would be an impact and greater trade. The relationship between freight and GDP is an important topic for both strategic transport planning and the demand estimates needed for feasibility studies that underly investments work hundreds of millions of dollars to improve China’s road, rail, port, and airport infrastructure. Besides, factors outside the zones affect freight transport and GDP within a zone. For example, there is trade between economic zones in China. Most imports and exports, in terms of volume, are handled by ports on the east coast. While some of that cargo is only transported in the respective zones, others are originated or destined to other economic zones.
Based on the above conclusions and discussions, the following policy recommendations have been put forward to further promote the sustainable development of freight transport and economic system.
(1) If the objective is to promote economic growth in the Northeast, Circum Bohai-Sea, Southwest and Northwest economic zone, then the investment in transport infrastructure would then be of great benefit, as a causal relationship from freight turnover to economic growth has been found. Focusing and investing directly in the promotion of economic development could be a better option for the transportation industry in the Pearl River and Middle Part economic zone.
(2) The transport infrastructure construction in the Middle Part and Northwest economic zone should be strengthened, and the cargo trade relationship with other zones should be increased. Economic policy should be emphasized to form a mutual promoting situation between GDP freight turnovers to promote their economic development. The Freight communication between the Northeast economic zone and other economically developed zones should be strengthened to maintain its economic growth. For the Pearl River economic zone with developed transportation, the transportation and economy can be maintained at the current development level.
(3) Several implications can be drawn from a broader sense, which can provide some references for coordinated development between transportation and economic systems for other economic zones. For the economic zones with a large share of the national GDP, the basic principle of freight development is to maintain the current level of transportation infrastructure and increase freight exchanges with other economic zones. Also, the various transport means should be through the government-led and market integration, efforts to build intensive operation, clear division of labor and complementary functions of the transport system, which will speed up the growth of the economy. For the less-developed economy, the development of freight transportation in these areas has a considerable impact on the GDP of the country. The traffic infrastructure construction and the historical problems of these areas should be given special attention to promoting economic development. For the already-built rural roads, the demand for daily maintenance and repair should be met for ensuring good conditions to realize the sustainable development of freight transportation and the economy.
China is in the new normal of medium to high-speed economic growth in the near future instead of high-speed economic growth in past decades. Transportation is a crucial area to expand domestic demand and serve steady economic growth. How to promote sustainable development between transportation and economy system effectively is a new test under the background of the strong transportation network in the new era. The examination of causality direction between them precisely is beneficial to provide sustainable development policies and promote the coordination of the zonal economy and transportation.
The economic indicator used in this paper is GDP, and the transportation indicator is freight turnover. In the future, other variables such as national GDP growth rate, the size of each zone, and some sort of factor to act as a proxy for developments in neighboring zones could be considered and expanded to examine the direction of causality more precisely.