A Behavioral Interpretation of Volatility Patterns in Brazilian Stock Market: Analysis of Pre and Post-COVID-19 Periods from 2019 to 2021

There has recently been an increasing number of new investors in the Brazilian stock markets, providing new asset allocation opportunities as well as challenges in terms of individual judgment and decision-making. The departure point of this paper is the conjecture that the Ibovespa (Brazilian stock exchange index) might reveal asymmetric volatility patterns during the January 2019 to February 2021 period that call for behavioral financial explanations. More specifically, this paper aims to subject this bold conjecture to an empirical test. It draws on a threshold autoregressive conditional heteroskedasticity (TARCH) model to investigate the existence of asymmetric reactions in the period under study. Our findings suggest that the traditional approach to finance fails to explain volatility patterns in the Brazilian stock market behavior, since they do not fit well with predictions based on the efficient market hypothesis. Inspired by Vasileiou’s (2021) account of what occurred with the New York Stock Exchange during COVID-19, we then embark on a brief survey of the vast literature on applied behavioral economics and finance to provide an interpretation of the heuristics and biases that may be non-negligible mental mechanisms underlying the Ibovespa’s detected asymmetric responses.