Ownership Structure and the Leverage–Performance Nexus: Evidence from BIST Energy Firms Using Panel Data and Double Machine Learning

This study completes the analysis of a firm’s performance and its financial leverage in the Turkish energy industry along with the ownership between family-run and non- family-run firms. The research uses financial data of listed firms in the Istanbul Stock Exchange over Q1 2021 - Q3 2025 with quarterly frequency to evaluate the influence of a firm’s leverage ratio on its profitability performance and volatility of profitability by way of a two-phase methodology. The first phase of the analysis uses a two-way fixed effects model to estimate the causal relationship of intra-firm time-related variability of company performance based on the company’s leverage. The second phase of the analysis employs Double Machine Learning (DML) as a robustness test of the outcomes of the first phase. Findings show that the impact of a firm’s financial leverage is found to be very different for firms along the family business and family business ownership lines. Family businesses tend to have less volatile performance and more stable financial structures when using leverage compared to non-family businesses. Conversely, using leverage increases the volatility and financial risk of non-family businesses. Performance and leverage levels also show a negative correlation in family businesses, but a positive correlation in non-family businesses. This research highlights the need for future research on how financial leverage and performance relate through an analysis of non-linear structures and unobservable heterogeneity; while also emphasizing the fundamental role that family ownership plays in risk management and financial stability, particularly in developing countries