5.2.1. Variable Setting
(1) Explained Variable
Green TFP(GTFP)
(2) Explanatory Variable
Industrial structure upgrading index (TS): in this index, the ratio of the tertiary industry output value to the secondary industry output value is used to measure the industrial structure upgrading index.
(3) Threat Variable
The industrial structure rationalization index (TL) is measured by employing the industrial structure synergy coefficient as follows:
where i represents industry, Y represents gross production, Y
i /Y represents the proportion of the output value of department I in total, and L
i/L represents the proportion of the number of employed people in sector I to the total number. The value range of TL is 0–1. The closer TL is to 1, the better the synergy between the change of employment structure and the change of industrial structure in an economy, and the higher the degree of industrial structure rationalization.
(4) Control Variables
Referring to existing literature, this article selects five control variables. Education level (EDU) refers to the higher education level of the resident. It is generally believed that a higher average level of education is more conducive to promoting technological progress and innovation, thereby facilitating economic development. The ratio of the sum of students in common colleges and universities to the total population is selected to measure the level of education. The financial development level (FI) refers to the ratio of total social financial activities to total economic activities in a given period. Financial development mainly affects the conversion efficiency of savings and investment and affects the scale and speed of monetary capital accumulation, thus changing the flow direction of industrial capital, the allocation structure, and the allocation of production factors. As a result, it has an influence on the industrial structure. The ratio of the sum of bank deposits and loans to GDP is selected to measure the level of regional financial development. The fixed asset investment rate (IN) is measured through the proportion of fixed asset investment in GDP. The urbanization rate (CZ) and Internet penetration rate (IP) directly use the statistical index values of the National Bureau of Statistics.
5.2.2. Empirical Results
This paper used Stata 16 software to estimate the model successively with a single, double, and triple threshold. For the F test of the single threshold, the null hypothesis means that there is no threshold, and the null hypothesis of the double threshold is that there is one threshold, and so on. The result shows in
Table 2.
As shown in
Table 2, in the single threshold effect test, the F statistic is 1.93, and the
p value is 0.83. In the triple threshold test, the F value is 2.27, the
p value is 0.655, and the null hypothesis cannot be rejected at a significance level of 0.1, showing that there are not one or three threshold values. In the double threshold test, the F value is 12.64, while the
p value is 0.09. The null hypothesis is rejected at the significance level of 0.1, showing the existence of the double threshold value. In this case, the regression equation is determined as follows:
An LR test was conducted according to Equation (10) of the regression equation, and the threshold parameter results are shown in
Figure 1. There were two threshold values in the sample, and the specific values are shown in
Table 2.
Figure 1 and
Table 3 show that upgrading industrial structures influences the green TFP, and the size of the industrial structure rationalization is separated into three phases: the first phase of the industrial structure rationalization is less than 0.661, the second phase of the industrial structure rationalization is greater than 0.661 and less than 0.673, and the third stage for the rationalization of industrial structure is greater than 0.673.
The reasonability of piecewise consideration can be determined by combining the panel threshold regression model with the panel model’s R
2 for comparison. R
2 of the threshold regression model is determined to be less than R
2 of the panel model, which indicates that the panel model is reasonable and cannot be used for piecewise research; otherwise, the threshold model is more reasonable. The results are displayed in
Table 4.
The results of the F value test and the Hausman test show that the
p value is equal to 0, indicating that the panel model should choose the fixed-effect panel model, and R
2 of the two models is compared; it can be found that the fixed-effect model is lower than the threshold regression model, indicating that the threshold regression model is more reasonable. The threshold regression results are displayed in
Table 5.
On the basis of the panel threshold regression results obtained in
Table 5, it is shown that there are double thresholds within the sample interval. When the rationalization index of the industrial structure is less than 0.661, there is a significant negative relationship between industrial structure upgrading and green TFP at the significance level of 0.10, and the regression coefficient is −1.485. When the industrial structure rationalization index is greater than 0.661 and less than 0.673, there is a significant positive relationship between industrial structure upgrading. When green TFP is at the 0.01 significance level, the regression coefficient is 11.625. When the rationalization index of the industrial structure is greater than 0.673, there is a significant negative relationship between industrial structure upgrading. When green TFP is at the 10% significance level, the regression coefficient is −0.394. The effect of the industrial structure upgrading on green TFP is initially negative, and then positive and negative, which means that when the rationalization degree of the industrial structure is at a relatively low level, the improvement of advanced levels of industrial structure affects the improvement of green total factor productivity. At this stage, the industrial structure foundation is poor, the structure of various industries is not coordinated, and the overall development is not balanced in underdeveloped areas. Meanwhile, there is no reasonable basis for industrial structure development, and the adjustment thinking of industrial policy in underdeveloped areas should not focus on the improvement of advanced levels of industrial structure; otherwise, the green TFP will be affected. When the industrial structure rationalization index is greater than 0.661 and less than 0.673, high-level industrial structures and green TFP display a significantly positive relationship, which shows that with a high degree of industrial structure rationalization, high-level industrial structure development promotes green TFP significantly in underdeveloped areas. In the stage of relatively reasonable allocations of resources among industries, the industry-coordinated development degree is higher, and the industry’s output achieves an improved balance among workers. The growth of the secondary industry lays a good industrial foundation and driving force for the further development of the tertiary industry. Based on this, the economic growth can move in the service-oriented direction, and the development of green TFP can be accelerated by vigorously improving industrial structure. When the industrial structure rationalization index is greater than 0.661, a clearly negative relationship below the 0.10 significance level exists between the high-level industrial structure and green TFP. This stage indicates that the industrial structure rationalization degree is higher than equilibrium (0.673), further improving the level of industrial structure upgrading, rationalization, the green economic development in underdeveloped areas, and the level-shift-inhibiting effect.
The rationalization indexes of industrial structure in underdeveloped areas are mostly in the first interval. When the industrial base is weak and the level of rationalization is low, if the underdeveloped areas excessively pursue industrial structure upgrading, the unbalanced investment of factor resources may affect the good interaction between the three industries, thus affecting the quality of industrial economic development.
The control variable financial development degree (FI) has no obvious influence on the green TFP advancement. Finance is the core of modern economy. It has an influence on green TFP through five aspects: capital formation, capital allocation, credit creation, information disclosure, and risk prevention and diversification, and it plays an important role in optimizing resource allocation and promoting optimization of green TFP. This may be due to the relatively low level of financial development in underdeveloped areas, which failed to play a role in advancing green economic growth.
The control variable education level (EDU) has a significantly positive effect on green TFP. From the perspective of consumption, improvements in education levels will change the structure of product consumption demand to some extent and then stimulate green TFP increase.
The coefficient of the fixed-asset investment rate (IN) of the control variable is significantly negative, showing that the fixed asset investment is not enough to promote green TFP. Fixed-asset investment is an important means of resource allocation, and the scale and structure of investment play a decisive role in regional green TFP. The economic development of underdeveloped areas mainly depends on investment, which determines the industrial composition of economic growth, and the proportion of investment in the three industries decides the output proportion of the three industries. The fixed asset investment in underdeveloped areas has a negative influence on green TFP, which indicates that the investment structure is unreasonable, emphasizing the mode of heavy industry development and affecting the improvement of green TFP.
The influence of the control variable urbanization rate (CZ) on green TFP is significantly positive. Urbanization in underdeveloped areas is still at a relatively low level, and the process of urbanization can effectively promote economic growth.
The influence of the control variable network penetration rate (IP) on green TFP is significantly negative. Network economy is a new type of economic form, and its development is affected by many factors, including capital, market, and technology. A region’s economic development affects the development of Internet penetration, and as the quality of the network economy in underdeveloped areas is still at low levels, internet penetration ascension failed to advance the coordinated development of industry and service industry and has an inhibitory effect on green TFP.