محمد احدزاده

This study investigates the impact of the board's social capital on the investment efficiency of listed companies in the Tehran Stock Exchange. Based on the theoretical foundations, the board social capital as a social-behavioral factor can affect the problem of over or under-investment (both of which are examples of the inefficiency of investment decisions). Therefore, when the board's social capital is at a high and favorable level, company managers show less opportunistic behavior and do their best to increase cooperation and interaction within the company, which leads to the strengthening of investment efficiency. In terms of purpose, the current research is the applied-developmental type and takes a descriptive-correlational manner. We measured board social capital using the Co-Working Experience index. Investment efficiency is also measured through under- and over-investment using the Richardson (2006) model. The control variables also include the size of the board of directors, the independence of the board of directors, the size of the company, the ratio of net profit to sales, the rate of return on assets, and the level of financial leverage. The statistical population of the research includes 183 companies admitted to the stock exchange from 2016 to 2022. In order to test the research hypothesis, a multivariate regression model has been fitted using the panel data method with the fixed effects approach. The results of the research indicate that the hypotheses of the research are confirmed, and there is a positive and significant relationship between the social capital of the board of directors and investment efficiency.

Herd behavior, the tendency of individuals to mimic the actions of a larger group, significantly impacts capital markets by influencing stock prices, market liquidity, and overall market stability. This phenomenon has garnered significant attention in financial studies due to its implications for both institutional and individual investors, contributing to increased market volatility and potential crashes. Various methodologies have been developed to assess herd behavior, revealing its presence across diverse market conditions, including periods of high distress and volatility. This study examines macro herding in the Tehran Stock Exchange from March 2016 to February 2024, using weekly asset returns to measure herd behavior among listed companies. For the first time in Iran, we employ the TV method to calculate herding. The TV method offers two primary advantages: it is adept at identifying macro herding because it captures the collective trading direction of investors, and it operates independently of asset pricing models, minimizing biases associated with those models. Focusing on the collective trading direction, we aim to detect significant deviations in stock price movements indicative of herd behavior. Our findings indicate that herd behavior is more pronounced during extreme market conditions, both positive and negative, with a particularly notable increase during periods of negative market returns. This study provides insights into the dynamics of investor behavior in the Tehran Stock Exchange, highlighting the importance of monitoring such behavior to mitigate its potential adverse effects on market stability.