5.1. Baseline Regression
As panel data are utilized, a Hausman test was first carried out. The result, with a
p-value of 0.0007 for the chi-squared statistic, rejects the null hypothesis, indicating the appropriateness of the fixed effects model. Columns (1)–(5) in
Table 4 present the regression results examining the impact of NQPF on GTFP, with control variables introduced progressively. The estimated coefficients for NQPF remain positively signed and achieve statistical significance in every model specification, irrespective of whether control variables are added. This outcome is consistent with our theoretical expectations and offers empirical validation for Hypothesis 1.
This beneficial impact can largely be ascribed to the inherent characteristics of NQPF, which is driven by technological innovation, informatization, and intellectualization. The technological advancements inherent to NQPF facilitate a shift away from traditional production models marked by intensive energy use and substantial emissions. This transition enhances resource utilization efficiency while mitigating negative environmental impacts, thereby ultimately elevating GTFP.
Among the control variables, some demonstrate statistically significant effects. The coefficient for Foreign Direct Investment (FDI) is significantly negative across multiple model specifications. This finding may correspond to the “Pollution Haven Hypothesis” proposed in the existing literature, suggesting that in certain periods or regions, inward FDI may concentrate in energy-intensive or high-emission industries or introduce relatively outdated technologies, thereby exerting a certain inhibiting effect on local GTFP [
32]. Conversely, the coefficient for Environmental Regulation (ENV) is significantly positive, indicating that increased investment in industrial pollution control effectively promotes the improvement of GTFP. This is consistent with the “Porter Hypothesis,” contending that suitably designed environmental regulations could encourage enterprises to engage in green technology innovation and seek efficiency gains [
33]. The directional effects of other control variables are generally consistent with prior research, collectively supporting the reasonableness of the model specification.
Given that Column (5), which includes the full set of controls, demonstrates the best model fit, it is designated as our baseline specification for the subsequent robustness checks and heterogeneity analysis.
5.2. Robustness Checks
To verify the stability of the main regression findings, this research performs multiple checks, such as applying a one-period lag to the key explanatory variable, trimming extreme data points, and adopting a different measure for the outcome variable.
5.2.1. One-Period Lag of the Core Explanatory Variable
Applying a one-period lag to the primary explanatory variable serves to alleviate possible endogeneity arising from reverse causality and more effectively captures the sustained influence of NQPF. The lagged NQPF continues to generate a statistically significant positive influence on GTFP at the 1% level, evident in the first column in
Table 5. This finding not only corroborates the positive relationship identified in the baseline analysis but also suggests that the effect of NQPF on GTFP exhibits a degree of persistence.
5.2.2. Winsorization
To counteract the possible distortion caused by extreme values in the sample, all continuous variables were winsorized at both the 1st and 99th percentiles. The regression outcomes using this trimmed dataset are shown in Column (2) of
Table 5. The persistently positive and significant coefficient for NQPF indicates that the central result is robust and not attributable to outlier influence.
5.2.3. Alternative Measurement of the Dependent Variable
Departing from the baseline measurement, an alternative GTFP measure (denoted as DGTFP) is constructed. First, to create a single composite measure, the entropy method is employed to integrate data on industrial wastewater discharge, industrial SO
2 emissions, and general industrial solid waste. This composite indicator is then incorporated into the GTFP calculation. As evidenced in the third column in
Table 5, NQPF’s estimated coefficient stays positive and reaches 1% statistical significance, thereby strengthening the validity of core findings.
5.2.4. Change the Measurement Method of Core Explanatory Variables
To test whether the research conclusions depend on specific measurement methods, this study reconstructs the core explanatory variable using the following two approaches and conducts robustness checks:
The principal component analysis (PCA) method is used to reconstruct the composite index of New Quality Productivity. This approach reduces dimensionality by extracting principal components with eigenvalues greater than one, retaining essential information while mitigating multicollinearity issues. After standardizing the indicators, PCA is performed, and an index (labeled PCA.NQPF) is constructed by weighting components according to their variance contribution rates. This index is then reintroduced into the baseline model for re-estimation.
To avoid conceptual overlap between NQPF and GTFP, all environment-related indicators are excluded when constructing the NQPF index for sensitivity analysis. Based on the streamlined indicator system, the entropy weight method is applied again to compute a new index (labeled EX.NQPF), followed by further regression analysis.
The results show that whether using PCA.NQPF or EX.NQPF, the impact of NQPF on GTFP remains significantly positive, with coefficient directions consistent with the baseline findings. This indicates that the core conclusions are robust across different measurement methods and do not rely on a specific index construction approach.
5.2.5. System GMM
To address endogeneity concerns and verify the robustness of the findings, we further employ the System GMM method for estimation. Following the standard approach for dynamic panel models, we use the first lags of the dependent variable (GTFP) and the lagged levels of the endogenous regressors (NQPF) as instruments in the difference equation, and the lagged differences as instruments in the level equation. The first lag of the dependent variable (L.GTFP) is utilized as an instrumental variable in the GMM regression. The sixth column in
Table 5 demonstrates that after accounting for the long-term effects inherent in GTFP and mitigating endogeneity, the regression coefficient of NQPF on GTFP remains significantly positive at the 1% level. The model passes both the Arellano-Bond test for autocorrelation and the Hansen test for over-identification, confirming the validity of the instruments and the absence of serial correlation. Therefore, the positive promoting effect of NQPF on GTFP is robust, and the conclusions are not compromised by endogeneity issues.
5.2.6. Change the Depreciation Rate of Capital Stock
In the baseline regression, this study adopts a fixed depreciation rate (
δ = 9.6%) commonly used in the literature to estimate capital stock. To examine the sensitivity of the core findings to this parameter setting, we further re-estimate the capital stock using two different depreciation rates, 5% and 10%, and re-run the regression analysis. As shown in Columns (7) and (8) of
Table 5, under different depreciation rate assumptions, the promoting effect of NQPF on GTFP remains positive and significant, with no substantial changes in the coefficient magnitude or statistical significance. This indicates that the research conclusions of this paper are not sensitive to the setting of the capital depreciation rate and demonstrate good robustness.
5.5. Threshold Effects
The preceding analysis demonstrates that cultivating NQPF can significantly enhance GTFP. A pertinent question, however, is whether this causal effect is subject to conditioning by other factors. As suggested by Hypothesis 3, the level of GFD represents a potentially significant threshold variable. We proceed to empirically test this possibility.
First, we employ the bootstrap method developed by Hansen (1999) [
25] to test for the existence of a threshold effect using the GFD level as the threshold variable. The findings, displayed in
Table 8, demonstrate that the specification employing green finance as the threshold variable satisfactorily meets the criteria for a double-threshold effect.
In
Table 9, the two estimated threshold values for the GFD level are 0.2695 and 0.4530, respectively.
Figure 4 additionally graphs the likelihood ratio (LR) function for the dual-threshold model, with the dashed line marking the 95% confidence critical value. The outcomes reveal that the LR statistics corresponding to both threshold estimates lie beneath this critical line, affirming that the identified thresholds possess statistical significance and validity.
The threshold regression results are displayed in
Table 10. When the GFD level is at or below the first threshold value of 0.2695, NQPF’s impact on GTFP is not statistically significant. However, when the GFD level surpasses the first threshold but remains below the second threshold (i.e., within the interval [0.2695, 0.4530)), NQPF begins to exert a significant positive influence on GTFP, significant at the 1% level. To be specific, a one-standard-deviation increase (0.110) in NQPF leads to a 0.239 percentage-point rise in GTFP (=2.169 × 0.110). Furthermore, as the GFD level continues to increase and surpasses the second threshold of 0.4530, the significant positive impact of NQPF on GTFP persists. In this high regime, a one-standard-deviation increase (0.110) in NQPF results in a 0.315 percentage-point increase in GTFP (=2.860 × 0.110), indicating a pattern of increasing marginal effects. Therefore, Hypothesis 3 is supported.
A plausible explanation for these findings is as follows. When GFD is at a low level, green industries within the region face challenges in obtaining adequate and targeted financial support, leading to binding financing constraints. This not only intensifies operational pressures for relevant enterprises but also hinders the cultivation of green technologies. Consequently, NQPF fails to demonstrate a significant effect on GTFP at this stage.
As the development of green finance improves, more capital is directed toward green, environmentally friendly, and sustainable projects. This enhances resource allocation and boosts investment in green technologies, thereby driving green technological innovation. Given that NQPF itself is inherently oriented toward technological innovation and green advancement—often termed “green productive forces”—its sustained development is effectively supported by a more developed green finance system. This synergy ultimately leads to higher GTFP.
With further advancement in GFD, the interaction between green finance and NQPF may enter a phase characterized by the superposition of scale effects and structural effects. This phase facilitates the transition of NQPF from mere technological breakthroughs to systematic industrial upgrading, promotes the formation of green industrial clusters, and amplifies technological spillovers. As a result, the impact of NQPF on GTFP exhibits the characteristic of continuously increasing marginal effects.
An analysis of the sample data from 2023 reveals distinct regional patterns in the development of green finance. Five provinces, all located in Western China (namely Inner Mongolia, Yunnan, Qinghai, Ningxia, and Xinjiang), had not yet surpassed the first threshold value. Nine provinces were positioned between the first and second thresholds, comprising two from Eastern China (Tianjin, Hainan), four from Central China (Shanxi, Anhui, Jiangxi, Henan), two from Western China (Chongqing, Sichuan), and one from Northeast China (Jilin). Sixteen provinces had crossed the second threshold, including eight from Eastern China (Beijing, Hebei, Shanghai, Jiangsu, Zhejiang, Fujian, Shandong, Guangdong), two from Central China (Hubei, Hunan), four from Western China (Guangxi, Guizhou, Shaanxi, Gansu), and two from Northeast China (Liaoning, Heilongjiang). This distribution indicates that all provinces in the Eastern, Central, and Northeast regions have surpassed the first threshold. Notably, the majority of provinces in the Eastern and Northeast regions have crossed the second threshold, whereas nearly half of the provinces in Western China remain below the first threshold of GFD.
Following the empirical tests conducted, including benchmark regression, robustness tests, mechanism identification, and threshold effect analysis, all three research hypotheses proposed in this study have been fully validated. To clearly present the correspondence between the empirical results and the research hypotheses, the hypothesis validation outcomes are summarized in
Table 11.
The results indicate that NQPF not only directly and robustly enhance GTFP but also exert an indirect promotional effect through the key pathway of incentivizing green technological innovation. Furthermore, the effectiveness of this promotional role significantly depends on the supportive environment provided by the regional level of GFD and exhibits a dynamic characteristic of increasing marginal effects as this level improves.