BİST Sürdürülebilirlik Endeksinde yer almanın ve kurumsal yönetim ilkelerinin şirketlerin finansal performansı üzerindeki etkisi

This study explores how corporate governance performance and sustainability index participation relate to the financial performance of companies listed on Borsa Istanbul (BIST). Utilizing a firm-level panel dataset covering the 2014–2023 period, the analysis was conducted using the Fama-MacBeth regression approach. This method involves estimating cross-sectional regressions separately for each year and averaging the resulting coefficients over time, thereby accounting for firm-level heterogeneity while capturing time-specific effects. The models include Return on Equity (ROE), Return on Assets (ROA), and EBITDA (Earnings Before Interest, Taxes, Depreciation and Amortization) to Total Assets as accounting measures, while raw and alphas are considered as market-based outcomes. Independent variables encompass corporate governance performance, firm size (measured by market capitalization), systematic risk (beta), book-to-market (B/M) ratio, inclusion in the Sustainability Index Dummy (SIC), and prior-period returns. A total of twelve model specifications were employed, allowing for a comparative analysis of how the same explanatory variables relate to different dimensions of financial performance. This design provided a broader perspective on the ESG (Environmental, Social and Governance) performance nexus and helped assess the robustness of the results. The results show that market capitalization is generally associated with improved financial performance, especially in accounting-based models, although this effect is not consistently significant across all specifications. Corporate governance performance, on the other hand, displays mixed results. In several models, particularly those focused on ROE and EBITDA, higher governance scores are linked to lower short-term performance, which might reflect adjustment costs or lagged impacts. Although the cumulative return analysis suggests that the sustainability index appears to have outperformed the BIST100 over the sample period, the differences in returns are not statistically significant. Moreover, the SIC variable does not exhibit a consistent or statistically significant relationship with financial performance indicators, implying that inclusion in the sustainability index does not inherently result in superior short-term financial outcomes. These results may reflect the short-run costs associated with governance and ESG implementation. Measures such as reporting compliance, policy restructuring, and stakeholder transparency often lead to a rise in operational expenses, which can weigh on profitability and share performance in the near term. Nevertheless, these practices should not be assessed solely through a short-term lens. ESG-oriented strategies are often aimed at reducing long-term risks and improving investor confidence, which may contribute positively to firm value over time. Keywords: Corporate Governance Performance, ESG, Financial Performance, BIST Sustainability Index