Unit roots usually appear in time series data, resulting in pseudo regression. In order to avoid pseudo regression, this paper uses LLC test and IPS test to perform panel unit root test on the data before estimating the model. The results show that the variables are stationary.
4.1 Basic Regression Analysis
Models (1)-(2) in Table 3 are the estimation results of the formula (1). Model (1) uses green technological progress (GTP) as the explained variable. It can be seen that R&D coefficient is positive and significant at the 1% level, indicating that R&D investment can promote GTP in manufacturing industry, thus validating Hypothesis 1. This conclusion shows that during the sample period, China's R&D investment shows a certain green technological progress bias, and the main reason behind it may be the strengthening of environmental regulations. For example, the 11h Five-Year Plan (2006–2010) took the reduction of energy consumption per unit of GDP as a binding indicator. The 12th Five-Year Plan (2011–2015), while taking the reduction of energy consumption per unit of GDP as a binding indicator, put forward the requirement to reasonably control the total energy consumption. During the "13th Five-Year Plan (2016–2020)" period, the "double control" action of total energy consumption and intensity was implemented, and it was clearly required that by 2020, the energy consumption per unit of GDP should be reduced by 15% compared with 2015, and the total energy consumption should be controlled within 5 billion tons of standard coal. The 14th Five-Year Plan (2021–2025) further proposes to improve the dual control system of total energy consumption and intensity, and focus on controlling fossil energy consumption consumption. In 2025, the energy consumption per unit of GDP will be reduced by 13.5% compared with 2020. As a comparison, model (2) uses green technical efficiency change (GEC) as the explained variable, and it can be seen that R&D investment can also improve GEC. According to Schumpeter's innovation theory (Schumpeter 1934), innovation is to introduce a new combination of production factors and production conditions into the production system, that is, recombination of production factors. From the perspective of the microscopic mechanism, the process of promoting technological progress through research and development will involve the optimization of the entire production process of the enterprise, thereby reducing waste and improving green technical efficiency change.
Table 3
| (1) GTP | (2) GEC | (3) GTP |
R&D | 5.453*** (1.787) | 2.835*** (0.692) | |
ER | 0.606** (0.240) | -0.177 (0.159) | 0.619** (0.242) |
T2008 | -0.033*** (0.006) | -0.004 (0.006) | -0.032*** (0.007) |
R&D_1 | | | 15.98*** (3.895) |
R&D_2 | | | 10.15*** (2.205) |
R&D_3 | | | 6.096*** (1.382) |
Constant | 0.979*** (0.016) | 0.964*** (0.007) | 0.927*** (0.021) |
Industry fixed effect | Yes | Yes | Yes |
Time fixed effect | No | No | No |
Observations | 364 | 364 | 364 |
Note: ***, **, and * respectively indicate significance at the 1%, 5%, and 10% levels. Robust standard errors are in parentheses. |
In addition, environmental regulation (ER) can promote GTC, which further verifies the "Porter Hypothesis" (Porter 1991; Porter and van der Linde 1995), that is, environmental regulation can motivate enterprises to carry out green technology innovation. However, environmental regulation can inhibit the improvement of GEC, although the coefficient is not significant, which indicates that environmental regulation can reduce the efficiency of resource allocation to a certain extent (Tombe and Winter 2015). This is mainly because China usually implements output-oriented environmental regulation policies which limit the energy use or emissions per unit of industry output. It is more difficult for low-productivity industries to meet policy goals than high-productivity industries. Enterprises in low-productivity industries may sacrifice resource allocation efficiency in order to achieve policy goals. Considering that China's manufacturing industry is still "big but not strong", and low-productivity industries are still in the majority, so overall, environmental regulation will reduce green technical efficiency change, which is contrary to the conclusion of existing research (Han Chao et al. 2017; Li and Sheng 2018). The 2008 financial crisis caused a slight setback in green technological progress.
4.2 Threshold Regression Analysis
Applying the threshold regression model requires two basic tests: one is the threshold effect test, that is, to test whether there is a threshold effect. The other is the threshold parameter test, that is, to test whether the threshold parameter is significant. Specifically, the threshold effect test is carried out sequentially according to the absence of a threshold, the existence of 1 threshold, the existence of 2 thresholds, and the existence of 3 thresholds. The null hypothesis of the threshold parameter test is: \({H}_{0}\): \(\widehat{{\gamma }}={{\gamma }}_{0}\). When likelihood ratio test statistic\(\text{L}\text{R}\left({\gamma }\right)\le -2\text{l}\text{n}(1-\sqrt{1-\alpha })\), the null hypothesis cannot be rejected, where \(\alpha\) represents the significance level, and this paper takes 5%, then the critical value of the corresponding LR is 7.35 (Hansen, 1999).
Based on formula (2), the above two tests are carried out, and the results are shown in Table 4. It can be seen that the single threshold model is significant at the 10% significance level, the self-sampling p-value is 0.0933, and neither the double threshold model nor the triple threshold model is significant. At the same time, combined with the likelihood ratio function graph corresponding to each model, the confidence interval of a single threshold model is too large, so this paper believes that the double threshold model is more suitable for analysis.
For the double-threshold model, the two thresholds are 0.0071 and 0.0222, or 0.71% and 2.22% of R&D intensity, respectively. According to the above two thresholds, this paper divides R&D investment into low level (R&D ≤ 0.0071), medium level (0.0071 < R&D ≤ 0.0222), and high level (R&D > 0.0222). Table 5 shows the number of manufacturing industries in different R&D investment levels in different years. It can be seen that nearly half of China's manufacturing industry R&D investment has been at a low level for a long time, but since the "12th Five-Year Plan (2011–2015)" period, China has begun to implement an innovation-driven strategy, which has made the manufacturing industry increase R&D investment, and the number of industries at a low level has begun gradually decrease. By 2017, 12 industries were at low level, 14 were at medium level, and no industry was at high level. It can be seen that since the "12th Five-Year Plan (2011–2015)" period, the upgrading of China's manufacturing industry has been very effective. The overall manufacturing industry has begun to move from a low level of R&D investment to a medium level of R&D investment, but few industries have moved from a medium level to a high level. The level of momentum still needs to be strengthened.
Table 4
Model | F value | P value | Threshold Value | Critical Value |
Ⅰ | Ⅱ | Ⅲ | 1% | 5% | 10% |
single threshold | 11.68* | 0.0933 | 0.0222 | | | 18.8939 | 14.2345 | 11.4923 |
double threshold | 5.48 | 0.6567 | 0.0071 | 0.0222 | | 31.0096 | 19.4205 | 14.0653 |
triple threshold | 10.45 | 0.6833 | 0.0030 | 0.0071 | 0.0222 | 54.3284 | 42.9645 | 29.7276 |
Note: *, **, *** indicate significance at the 10%, 5%, and 1% levels, respectively, and the p value is the result of repeated sampling 300 times using the "bootstrap" method. |
Table 5
The number of manufacturing industries in each interval in different years
| 2004 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 |
low | 11 | 8 | 9 | 9 | 9 | 16 | 17 |
medium | 14 | 15 | 14 | 14 | 14 | 10 | 9 |
high | 1 | 3 | 3 | 3 | 3 | 0 | 0 |
| 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 |
low | 16 | 15 | 15 | 14 | 12 | 12 | 12 |
medium | 10 | 11 | 11 | 12 | 14 | 14 | 14 |
high | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Model (3) in Table 3 is the estimation result of formula (2). In model (3), R&D_1, R&D_2, and R&D_3 correspond to the R&D investment levels in three intervals: low level, medium level and high level, respectively. It can be seen that the R&D investment (R&D) coefficients of the three intervals are 15.98, 10.15, and 6.096, which are all significant at the 1% level, indicating that R&D investment can promote green technological progress in manufacturing industry. This is consistent with the estimation of the formula (1). However, as the level of R&D investment reaches a certain level, the promotion effect of R&D investment on the progress of green technology in the manufacturing industry decreases significantly, thus verifying Hypothesis 2, which explains the low level of R&D investment in China's manufacturing industry to a certain extent. When the level of R&D investment reaches a certain level, its promoting effect on the progress of green technology will be greatly reduced, and the motivation of enterprises to invest in R&D based on self-interest will decrease, so that the scale of R&D investment will be lower than the social optimal scale.