3.1. Descriptive Statistics and Jarque–Bera Test
Table 2 shows that the arithmetic means of the variables reflect noticeable differences in the financial and operational characteristics of the firms under study. The average leverage ratio (LEV) is approximately 0.154, with a standard deviation of 0.162, indicating considerable variation in firms’ reliance on debt financing. Similarly, the mean value of the debt-to-equity ratio (TD_EQ) is about 0.285, accompanied by a relatively high standard deviation (0.327), which points to substantial heterogeneity in capital structures across firms. Firm size (SIZE) records an average of 20.55 and a comparatively low standard deviation (1.65), suggesting a reasonable degree of homogeneity in firm size. Earnings per share (EPS) have a mean of 0.25 with a standard deviation of 0.36, reflecting notable fluctuations in profitability levels. The return on assets (ROA) shows a relatively low mean (0.035) and a standard deviation of 0.05, indicating limited dispersion in asset efficiency. Tangibility (TANG) has an average value of around 0.33 with a standard deviation of 0.24, implying moderate variation in asset composition. The growth rate (GRW) records a mean of 0.046 and a relatively high standard deviation (0.124), highlighting wide differences in growth performance among firms. Liquidity (LIQ) has an average of 0.58 with a standard deviation of 0.24, while cash flow (CASHFLOW) reports a mean of 0.097 and a standard deviation of 0.075, both indicating noticeable variability in firms’ short-term financial positions and cash-generating capacity. Regarding distributional properties, the skewness, kurtosis, and Jarque–Bera statistics consistently reject the assumption of normality for all variables at conventional significance levels. Nevertheless, the large sample size mitigates potential concerns related to non-normality, supporting the application of econometric models with appropriate robust standard error adjustments.
The frequency distribution of the COVID-19 variable, which is specified as a binary (dummy) variable taking the values 0 and 1, is based on a total of 1623 observations. The results indicate that the majority of observations fall under the value 0, with 1190 cases, representing 73.3% of the sample, whereas the value 1 is recorded for 433 observations, accounting for 26.7%. The equality between the Percent and Valid Percent columns confirms the absence of missing data for this variable, which enhances the reliability of the dataset. In addition, the cumulative percentage reaches 100% at the category 1, indicating full coverage of the sample. From a statistical perspective, the relatively unbalanced distribution suggests that non-COVID-19 periods (value 0) dominate the sample compared to periods affected by the pandemic (value 1). Such a pattern is commonly observed in longitudinal datasets that span several years before and during the COVID-19 outbreak. Consequently, this dummy variable is well suited for inclusion in regression and econometric analyses to capture the differential impact of the COVID-19 pandemic on the variables under investigation. The frequency distribution of the Industrial variable, which is defined as a binary (dummy) indicator capturing whether a firm belongs to the industrial sector or not, is based on a total of 1623 observations. The results show that most observations are concentrated in category 0, with 1352 cases, representing 83.3% of the sample, while 271 observations (16.7%) are classified under category 1. The identical values of the Percent and Valid Percent columns indicate that there are no missing observations for this variable, confirming the consistency and completeness of the data. Furthermore, the cumulative percentage reaches 100% at the final category, reflecting full sample coverage. From a statistical standpoint, this distribution reveals a relatively uneven representation of industrial firms compared to non-industrial firms within the sample, a pattern commonly observed in multi-sector datasets. Accordingly, this variable can be effectively incorporated into regression and econometric models to control for sector-specific effects and to examine the differential impact of industrial affiliation on the study variables.
3.5. Panel Generalized Method of Moments
Table 8 and
Table 9 shows that, according to the panel estimation model using least squares, it can be concluded that:
The independent variables that were accepted in the model (SIZE-EPS-ROA-TANG-GRW-CASHFLOW-LIQ-COVID-19-INDUSTRY) explain 81–74% of the total variation in the dependent variables ((Lev_TD), (TD_EQ)), and the remaining percentage is due to either the random error in the regression model or other independent variables excluded from the regression model.
The lagged value of the dependent variable (Lev_TD), (TD_EQ) exhibits a strong positive effect, indicating persistence in the model dynamics. Firm size (SIZE) also shows a positive and meaningful association, suggesting that larger firms tend to exhibit higher levels of the studied financial outcome. In contrast, earnings per share (EPS) do not appear to have a significant impact, implying a limited role in explaining the variation in the dependent variable during the sample period. Among the performance indicators, return on assets (ROA) demonstrates a significant negative relationship, which may reflect a tendency for more efficient firms to rely less on external financing. Asset tangibility (TANG) and growth opportunities (GRW) are positively and significantly related to the outcome, consistent with the idea that firms with substantial collateral or expansion prospects are more likely to engage in financing activities. Interestingly, cash flow (CASHFLOW) and liquidity (LIQ) are negatively associated with the dependent variable, indicating that firms with stronger internal funds or higher liquidity may depend less on the studied funding mechanism. Also, distinct patterns in leverage across the periods before, during, and after the COVID-19 pandemic were observed. In the pre-pandemic years (2013–2019), several coefficients, such as those for 2014 and 2016, indicate a slight decline in leverage, suggesting that firms adjusted their debt levels primarily based on internal factors like profitability, liquidity, and firm size, consistent with the Pecking Order Theory, where profitable companies rely more on internal financing. During the pandemic year of 2020, the leverage coefficient declines (−0.259448), although it is not statistically significant, reflecting a cautious approach as firms may have reduced debt or avoided additional borrowing due to heightened economic uncertainty. Following the pandemic (2021–2022), leverage begins to increase again, with the 2022 coefficient (0.027678, p = 0.0189) showing a statistically significant rise, indicating that firms gradually restored their debt levels to take advantage of financing opportunities and tax benefits, in line with the Trade-off Theory. Overall, these patterns demonstrate that leverage persistence over time reflects both internal strategic adjustments and responses to external shocks, highlighting the dynamic interplay between firm behavior and capital structure theories. The industrial sector variable also exhibits a positive effect, highlighting sectoral disparities. Temporal dummy variables yield mixed results, with only certain years showing meaningful effects, reflecting shifting economic conditions across the study period.
Variance Inflation Factors (VIFs) are considered important indicators for detecting the presence of multicollinearity among independent variables, as higher values reflect a greater severity of this issue. Some researchers suggest that a VIF value exceeding 10 indicates a serious multicollinearity problem, while others argue that this threshold is relatively high and recommend acceptable values to be below 4 or 5. Referring to the values presented in
Table 6 and
Table 7, it is evident that all VIF values are lower than 4, indicating that the proposed statistical model does not suffer from multicollinearity.
The test results indicate that the
p-value is lower than or equal to 0.05, leading to the rejection of the null hypothesis (H
0), which assumes that the residuals follow a normal distribution. Furthermore, the Pearson skewness coefficient, with a value of 0.28, falls within the acceptable range between −1 and +1, indicating that the data do not exhibit significant skewness (
Bluman, 2012).
Theil’s inequality coefficient (U) is employed to assess the predictive accuracy of the random-effect model. Its values range between zero and one, where a value of zero represents a perfect fit. The obtained values, which range from 0.15 to 0.19, are relatively close to zero, indicating a good level of model fit. Accordingly, the panel data model demonstrates a satisfactory goodness of fit, with an accuracy level ranging from approximately 74% to 81%.
The Durbin–Watson (DW) test is used to examine whether the residuals from an ordinary least squares (OLS) regression exhibit autocorrelation. Specifically, it tests the null hypothesis that the residuals are uncorrelated against the alternative hypothesis of positive first-order autocorrelation (AR(1)). The DW statistic ranges from 0 to 4, where a value close to 2 suggests no autocorrelation, values near 0 indicate positive autocorrelation, and values approaching 4 indicate negative autocorrelation. In this case, the observed DW values, ranging from 1.97 to 1.99, exceed the upper critical value (dU), implying that the null hypothesis cannot be rejected and the residuals can be considered uncorrelated.
The Breusch–Godfrey (BG) test was used to check for serial correlation in the regression residuals, which include key study variables such as TD_EQ(−1), SIZE, EPS, ROA, TANG, GRW, CASHFLOW, LIQ, COVID-19, and INDUSTRIAL, along with leverage dummies for 2013–2022. All p-values ranged from 0.2724 to 0.4643, above 0.05, indicating no evidence of serial correlation up to lag 2 and confirming the reliability of the estimated coefficients.
Many statistical methods, including ordinary least squares (OLS), rely on several underlying assumptions. A key assumption is that the variance in the disturbance term remains constant across observations, a condition known as homoskedasticity. When this condition is violated and the variance changes, the errors are described as heteroskedastic. Such variation can occur even when the error terms are assumed to originate from identical probability distributions.
To examine this issue, the Breusch–Pagan–Godfrey test was applied to the residuals of the multiple regression model. The results showed that the probability values associated with both the F-statistic and the Obs*R-squared statistic exceeded the 5% significance level. Consequently, the null hypothesis could not be rejected, supporting the conclusion that the error terms exhibit constant variance.
The Ramsey RESET test was employed to evaluate the correctness of the regression model specification. Since the significance levels of the t-test, F-test, and likelihood ratio test were all above 0.05 (0.3095–0.3574), the null hypothesis was not rejected, indicating that the model is correctly specified with no evidence of omitted variables or functional form misspecification.
The J-statistic is commonly applied in GMM and two-stage least squares frameworks to assess the validity of overidentifying restrictions. Given that the associated probability values range between 0.822565 and 0.93883, which are well above the 5% significance level, the null hypothesis is not rejected. This outcome supports the conclusion that the overidentifying restrictions hold and that the financial inclusion indicators used as explanatory variables can be considered exogenous.
The strength and validity of the instruments used in the estimation were evaluated using a weak instrument test. The Cragg–Donald statistic was calculated and compared with the Stock–Yogo critical values. The results indicated that the statistic surpassed the 7.03 threshold for the 5–10% significance level. This led to rejection of the null hypothesis that the instruments are weak, confirming that the chosen instruments are strong, reliable, and appropriate for producing valid regression estimates. Assessing instrument strength ensures that parameter estimates remain unbiased and conclusions are trustworthy.