درخت حوزه‌های تخصصی

Although theoretical and empirical literature regarding the stylized facts shows evidence of their correlations to herding behavior in financial markets, the causes of such phenomena are still unknown. Using an agent-based model strengthened by the competition co-evolution algorithm (STGP) technique, this study provides laboratory evidence on capital market dynamics and analyses the behavioral foundations of stylized facts such as fat tails, leverage effects, and volatility clustering. The simulated stock markets consist of two groups; the “Best agents”, which are a small portion of artificial agents, and the “Residual agents”, which are the main group of artificial agents. The best performance in terms of breeding fitness returns is the main feature of the “Best agents”. More, the size of the “Best Agents” group is specified as 2.5%, 5%, 10% &20% of the total population size. An agent-based model consists of two portions, a two thousand population of trader agents that each has its decision-making strategy, and a virtual market that creates the trading strategies. Then the model evolved step by step using a feed with real quotes of the financial instruments by Adaptive Modeler. A training period is considered 2500 bars (started in November 2003), and the test period started in December 2013. The observation shows that the herding behavior in the price series created by the “Residual agents” is less than the “Best agents” series. Therefore, the greater diversity of trade strategies as the genetic differences of artificial agents leads to less herding. The observations exhibit that the volatility clustering, leverage effects, and nonlinear dependence are more likely to experience in the price series generated by “Best gents”. Furthermore, observations indicate that if the population is well diversified in terms of trading strategies, the efficiency of the market increases.

In addition to imposing a negative impact on public health, Covid-19 has made the world face a huge financial-economic crisis. The worldwide spread of the coronavirus has also affected the volume of transactions and the value of stocks. Since the food market is more affected under crisis conditions, this relationship has been investigated in the stock exchange in the present study. In order to investigate the effect of Covid-19 patients on the stock index value of food industry companies as well as the relationship between risk and stock index value, the official daily data of the Ministry of Health and Medical Education and the Financial Information Processing Center of Iran were collected from March 3, 2021 when the first report was announced, to June 2, 2021. Mean Conditional heteroscedasticityvariance regression models were used in the current study. The statistical model specification tests showed that, first, the assumption of heteroscedasticitywas rejected and the needto useheteroscedasticitymodels was proved. Secondly, the asymmetry assumption was accepted. Model estimation results showed a relationship between the numbers of Covid-19 patients with the stock value of the food industry that was an increase in the number of infected people causes a decrease in the stock value of the food industry. Therefore, like other economic sectors, the capital market was affected by the Covid-19 crisis, and increasing exchange rate as a competing market had a negative effect on the stock price index. Also, considering the relationship between risk and stock value of food industries, as expected, there was an inverse and significant relationship between risk and stock value of food industry companies. In other words, an increase in risk leads to a decrease in the stock price of food industries.