4.1. Empirical results
To investigate potential cross-sectional dependence, heterogeneity, and nonstationarity issues in the data, we conducted several statistical tests addressing each of these concerns. Results for the tests of cross-sectional dependence (CSD) are presented in
Table 5. Cross-sectional dependence in panel data sets arises when observations or units exhibit correlation or interdependence across the cross-sectional dimension, potentially compromising the validity of statistical tests and yielding incorrect inferences. To assess the presence of cross-sectional dependence, we employed three tests: the Lagrange multiplier (LM) test proposed by Breusch and Pagan [
44], the cross-sectional dependence (CD) test developed by Pesaran [
45], and Pesaran’s [
46] LM cross-sectional dependence (CDLM) test.
Our findings indicate that the null hypothesis of no cross-sectional dependence can be rejected, revealing significant cross-sectional dependence in the data based on the p-values. This result supports the alternative hypothesis that cross-sectional dependence exists among OECD countries.
Upon establishing the presence of cross-sectional dependence for the variables and models, we proceeded to test for slope homogeneity. We employed two alternative tests for this purpose: Pesaran and Yamagata’s [
47] heteroskedasticity and autocorrelation consistent covariance (HAC) adjusted truncated slope homogeneity test (
), calculated using Blomquist and Westerlund’s [
48] HAC adjustment, and its small-sample adjusted counterpart (
). Both tests were conducted using pooled ordinary least squares regressions with five distinct model specifications, each featuring lggi as the dependent variable. While models 1 through 5 consistently included the variables lglo, lgdp, lpop, and ltemp, they differed in terms of the additional independent variable incorporated, with lcct, lco, lgov, lgtd, ltai, lfdi, ltax, and lepi being introduced separately across the different specifications.In order to check for the possible cross-sectional dependence, heterogeneity, and nonstationarity issues, we report relevant statistical tests for each of these. The statistical tests for cross-sectional dependence (CSD) are reported in
Table 5. Cross-sectional dependence in a panel data set refers to the presence of correlation or interdependence between the observations or units across the cross-sectional dimension of the data. This can occur when the observations are not independent of each other, which can affect the validity of statistical tests and lead to incorrect conclusions. To find the estimated results of the tests for cross-sectional dependence have been used three tests; the Lagrange multiplier (LM) test made by Breusch and Pagan [
44], the cross-sectional dependence (CD) test proposed by Pesaran [
45] and the LM cross-sectional dependence (CDLM) test proposed by Pesaran [
46]. The findings of the tests reveal that the null hypothesis of no cross-sectional dependence can be rejected and that a cross-sectional dependence exists with rejections at the traditional significance levels based on the
p-values reported in
Table 5. The acceptance of the alternative hypotheses provided evidence for the existence of cross-sectional support among OECD nations. The detection of cross-sectional dependence in the panel data suggests that shocks originating in one of the 38 countries may have propagated to the others due to their interconnectedness.
After the application of a cross-sectional dependency exists of the variables and models, the findings of testing whether a slope homogeneity exists or not are given. Thus, there are two alternative tests to determine slope homogeneity. The first test is by Pesaran and Yamagata’s [
47] truncated slope homogeneity (
) test with Blomquist and Westerlund’s [
48] heteroskedasticity and autocorrelation consistent covariance (HAC) adjustment. The second test is an adjusted version of the
test for small samples, designated by (
. Each test is constructed using a pooled ordinary least squares regression with five different model specifications. In each model, lggi is the dependent variable. Moreover, each of the models 1 to 5 includes the variables lcct, lfdi, lglo, lgov, lpop, ltax, and ltemp, but each also includes one of the variables lco, lgdp, lglo, lgtd, and ltai as independent variable, respectively.
Table 5 also presents the results from the slope homogeneity test. This test examines whether the relationship between variables remains consistent across all courtiers or if there are variations that warrant consideration in the analysis. The null hypothesis of slope homogeneity across countries is not rejected at all traditional significance levels by both regular and adjusted homogeneity tests, implying that the slopes do not vary across countries. Consequently, the impact of independent variables on economic growth appears to exhibit homogenous effects across the 38 countries under investigation. These findings suggest that the dynamic GMM estimation can be conducted without apprehension regarding slope heterogeneity, a crucial consideration as the GMM estimator becomes inconsistent for dynamic panel models in the presence of slope heterogeneity.
In light of the presence of cross-sectional dependence, this study employs second-generation panel unit root tests, which offer more reliable, consistent, and robust inferences in this case . The analysis aims to determine the stationarity of our variables using multiple panel unit root tests. Second-generation unit root tests typically enhance the conventional unit root test by incorporating cross-sectional dependence and additional variables or lags into the model, thereby improving the test’s power and reducing the likelihood of false positive or false negative results. The tests employed in this study include the cross-sectionally augmented Im-Pesaran-Shin test developed by Pesaran [
49], the modified cross-sectionally augmented Im-Pesaran-Shin tests proposed by Westerlund and Hosseinkouchack [
50], and the augmented Dickey-Fuller test also by Pesaran [
51]. These tests are denoted as CIPS, M-CIPS, and CADF, respectively.
The outcomes of the second-generation panel unit root tests, presented in
Table 6, predominantly reject the unit root null hypothesis with both constant and constant-trend specifications at the 1% and 5% significance levels. These findings indicate that all series are stationary at the level, with the exception of ltax, for which the CIPS and CADF tests do not firmly reject the unit root null at a constant level. However, the M-CIPS test concurs that the ltax variable is stationary at both constant and trend levels. Similarly, the lpop variable exhibits comparable behavior.
In alignment with model predictions, both country-time and fixed effects are observed, enabling the model to address the issue of unobserved country-specific heterogeneity. We examine the endogeneity of independent variables using the Durbin-Wu-Hausman technique, which applies two-stage least squares (2SLS) to panel data, and find that some variables exhibit endogeneity. To account for this, we follow Arellano and Bond’s [
52] recommendation of transforming the specified equations into first-difference estimators. Subsequently, we employ dynamic panel GMM estimators, which effectively mitigate concerns related to serial correlation, endogeneity and heterogeneity in the estimation process.
The two-step system GMM is a statistical method employed in commonly empirical estimation of econometric models that entails estimating the model in two stages. First, a GMM estimator is used, followed by the construction of a consistent estimator of the structural parameters. This approach enhances the accuracy and reliability of the estimates. Prior to conducting empirical estimation, two critical issues—proliferation of instruments and serial autocorrelation of error components—are examined. Baltagi [
53] contends that, in the presence of endogenous regressors, the system GMM estimator possesses the most desirable attributes for stationary dynamic panels with high cross-sectional (
) and short, fixed time (
) dimensions. This closely aligns with our context, which features
and
.
Table 7 presents the outcomes of the empirical analysis examining the relationship between green growth and the explanatory variables under consideration. Standard errors for the parameter estimates are displayed in parentheses beneath the corresponding estimates. For all estimated models, the null hypothesis of valid over-identification restrictions is not rejected at any conventional significance levels, thereby affirming the reliability of the instruments. Instrument proliferation does not appear to pose a concern, as the total number of cross-sectional units across all models exceeds the total number of instruments.
Considering the characteristics of the panel data framework, the dynamic system GMM estimation with one lag should not reject the existence first-order serial correlation according to the Lagrange multiplier Arellano-Bond test [
52]—LM-AR(1)—while rejecting the existence of second-order serial correlation AR(2) as per the LM-AR(2) test. The results of the LM-AR(1) tests in
Table 6 are all significant at the 1% level, corroborating the AR(1) specification. Conversely, several LM-AR(2) tests are not significant at the 5% and 1% levels across all models, rendering the AR(2) specification invalid. Consequently, all models are estimated with one lag of the dependent variable, signifying that an AR(1) dynamic specification is adequate for capturing autocorrelation. In addition to these observations, the Sargan test results do not reject the null hypothesis of valid over-identification restrictions at any significance levels for all estimated models, thereby confirming the validity of the instruments.
This study investigates the potential determinants of green growth, and six distinct models are estimated to evaluate their effects.
Table 7 summarizes the dynamic panel estimations for various model specifications of the green growth index. The first model illustrates the influence of economic performance, globalization, climate change adaptation, and green technology diffusion determinants on the green growth process, incorporating control variables for population and temperature. The coefficients of all determinants are positive and significant at all conventional significance levels, signifying a positive association with the green growth index. Green growth emphasizes enhancing economic productivity and efficiency while concurrently reducing the consumption of natural resources and minimizing waste and pollution. The positive relationship between green technology diffusion, economic growth, and climate change adaptation with green growth is crucial for realizing environmental sustainability. Green technologies contribute to the reduction of greenhouse gas emissions and other environmental impacts while simultaneously yielding economic advantages, such as increased efficiency and productivity.
Furthermore, adopting green growth policies can facilitate adaptation to the consequences of climate change, including rising temperatures and extreme weather events. For instance, investments in infrastructure resilient to flooding and other extreme weather occurrences can shield communities and businesses from the ramifications of climate change while concurrently yielding economic advantages. The results reveal a positive association between temperature and green growth.
Model 2 evaluates the influence of foreign direct investment on the advancement of green growth. The findings indicate a positive and significant relationship between foreign direct investment and green growth across all significance levels. In fact, foreign direct investment can foster green growth in several ways. First, it can grant access to capital, technology, and expertise essential for devising and executing green growth strategies. Second, foreign direct investment generates employment opportunities and stimulates economic growth, which can assist in amassing the resources required for investing in green growth. Third, foreign direct investment promotes international collaboration and partnerships, which can be instrumental in supporting green growth initiatives.
In Model 3, the impact of institutional factors on the progress of green growth is examined. The results reveal a positive relationship between government stability and green growth that is statistically significant at all conventional significance levels. Consequently, a stable and effective government can implement policies and regulations that encourage renewable energy, preserve natural habitats, and curtail greenhouse gas emissions. Moreover, a stable and effective government can facilitate the provision of essential infrastructure and services for sustainable development, including education, healthcare, and access to clean water and sanitation.
Model 4 presents the estimations of the impact of carbon emissions on green growth. The carbon emission coefficient is found to be positive and statistically significant at all conventional significance levels. In fact, green growth denotes environmentally sustainable economic growth, while carbon emissions are a primary contributor to climate change. A positive relationship between carbon emissions and green growth suggests that economic growth and environmental sustainability might be mutually exclusive. One rationale is that elevated levels of economic growth often result in increased carbon emissions. Another reason is that carbon emissions are a significant driver of climate change, which poses considerable risks to both economic growth and human well-being. Indeed, Model 4 illustrates a trade-off relationship. As a country prioritizes achieving high levels of economic growth and enhancing its green growth index score, it may have fewer resources to allocate to climate change adaptation measures. Additionally, escalating carbon emissions have a disastrous and substantial influence on climate change adaptation. Consequently, mitigating carbon emissions is of paramount importance in adjusting to the evolving climate.
Model 5 incorporates the environmental performance index, technology innovation, and environmental taxes into the green growth model. Notably, the CO2 variable cannot be included in this model due to the high correlation among these variables, stemming from the nature of the economy or the inclusion of a variable in an index variable. For instance, carbon emissions (CO2) constitute a sub-component of the EPI variable. The technology achievement index exerts a positive, significant impact, and a substantial contribution to the green growth index. This highlights the role of technology transfer in amplifying the effects of green growth among countries, as the development and adoption of new technologies are instrumental in promoting sustainable economic growth. Conversely, the environmental performance index and environmental taxes exhibit a positive and significant correlation with the green growth index. These observations underscore the significance of environmental concerns and policies in realizing green growth. Consequently, all variables in this model contribute to the progress of green growth.
Lastly, Model 6 presents the most comprehensive model by incorporating all determinants into a single equation, with the exception of globalization due to its high correlation with other variables. The model combines economic, technological, institutional, and environmental variables. The results are largely consistent with those obtained from individual equations. While carbon emissions have a detrimental impact on climate change adaptation, as observed in Model 4, they exhibit a negative and insignificant effect in Model 6. All other determinants contribute positively to the progress of green growth. In terms of marginal effects, the combined equation in Model 6 reveals that the variables exert greater marginal impacts compared to individual ones. We conclude that economic growth, population, carbon emissions, and temperature are the primary contributors to the green growth process.
4.2. Discussion
In this study, the determinants of green growth were analyzed empirically, considering various factors such as globalization, diffusion of green technologies, climate change adaptation, economic performance, environmental and political values, climatic conditions, and technological achievements of nations. The investigation was conducted using a comprehensive panel data set encompassing 38 OECD economies.
The empirical findings of our study reveal statistically significant and positive associations between green growth and an array of factors considered, such as green technology diffusion, income level, globalization, climate change adaptation, government stability, foreign direct investment, carbon emissions, environmental performance and taxes, technological achievements, population, and temperature level. These relationships are observed in the context of sustainable development within the selected countries. However, an intriguing observation was made regarding the impact of climate change adaptation, which exhibited a negative and insignificant effect on green growth when accounting for carbon emissions in models 4 and 6. This outcome suggests that carbon emissions pose a detrimental and significant influence on the progress of climate change adaptation efforts.
Firstly, in a complimentary context to our findings, Georgeson et al. [
54] propose a policy framework for fostering green growth in both developing and developed economies, emphasizing the significance of economic, political, social, technological, and environmental approaches for transforming the green growth process. Consequently, enhancements in these aspects may facilitate the advancement of green growth. Primarily, a country’s income level serves as a crucial factor in promoting green products and sustainable development. Anser et al. [
41] identify a causal relationship between GDP growth and carbon emissions, as well as a bidirectional causality between economic growth and energy usage. In a similar vein, Chin et al. [
22] report a positive association between economic growth and CO2 emissions. Concurrently, several studies [16,18, 21-23,30,36] have concluded that the influence of income level, CO2 emissions, environmental performance, climate conditions, and innovations enhance the green growth process.
Secondly, the foreign direct investment profiles of countries play an essential role in the adaption of the green growth process. Ayamba et al. [
55] conclude that there is an insignificant effect of investments on environmental quality in the long run, but that pollution variables have a significant negative effect on investments in the short run. Zafar et al. [
32] indicate that open trade and FDI have significant positive impacts on green growth both in the short and long run. Likewise, Ochoa-Moreno et al. [
56] conclude that investments enhance CO2 emissions in the long run in Latin American economies. Lastly, Khan et al. [
15] show significant causal relationships between policies of exports and imports, income level, and green innovation that has resulted in changes to consumption-based CO2 emission levels in G7 countries. In contrast, Tawiah et al. [
14] find mixed results among developed and developing countries the links between trade openness and FDI with green growth are negative and insignificant for developed nations, whereas the influence of trade openness and FDI on developing countries is negative and significant. These findings are comparable to the conclusion of Shahzad et al. [
57] on selected developed and developing countries. In this respect, our results are complementary to the empirical evidence presented in these studies, but in a more extensive coverage of countries, which includes both developing and developed countries.
Thirdly, globalization have also a significant role in green growth. Ahmad and Wu [
58], find that globalization displays mixed effects. It induces ecological deterioration impact in the absence of its interaction with eco-innovation. On the other hand, Xia et al. [
12] imply a significant positive relationship between globalization and CO2 emissions, moreover, GDP growth has increased CO2 emissions. Our results are complementary to existing evidence on the effect of globalization on green growth, but they encompass more nations, including emerging and developed ones.
Fourthly, green technology diffusion, climate change adaptation, government stability, economic development, technological achievement, and environmental performance are particularly prominent factors shaping the green growth. According to Samad and Manzoor [
39], R&D expenditures, green technology, market size, and environmental taxation all have a substantial influence on green growth. Furthermore, Antal and Van Den Bergh [
20] find that to achieve both environmental and economic goals, it is necessary to minimize climate change effects and environmental risks in long-term sustainability. The result is in line with the findings of several studies, see, for instance, [
26,
30,
31,
60,
61,
62]. In contrast, He et al. [
59] conclude that environmental performance has an adverse effect on green growth in developing economies.
In summary, our empirical analysis underscores the positive contribution of green growth determinants in achieving a sustainable environment and development, as corroborated by the extant literature. However, our results extend beyond previous studies by incorporating a more comprehensive set of factors influencing green growth progress. Our investigation provides complementary evidence to prior research across an expanded range of time periods and OECD countries, encompassing both developing and developed economies. Most notably, our study is the first to establish that green growth does not independently emerge and diffuse from a country’s green technology diffusion and climate change adaptation efforts. Instead, factors such as green technology diffusion, climate change adaptation, economic growth, and technological achievement within a country serve as significant drivers in promoting green growth.