The role of expectations in the formation of the price bubble in the stock market

Analyzing the formation of bubble prices in stock market is the most important macro subjects in recent years. Due to this importance, in this study we use a DSGE model (developed by Castelnuovo and Nisticò, 2010) in order to study bubbles in stock market price index. Because the price bubble is a non-fundamental factor, using the approach of separating fundamental from non- fundamental factors is a good way to evaluate the formation of a bubble in the stock market. Accordingly, in this study, the variables of changes in inflation, production and stock price are separated according to fundamental and non- fundamental factors and then the effect of each of the non- fundamental shocks on macro variables such as stock price and stock price bubble formation is investigated. By calibrating the structural parameters of the model, the results show that non- fundamental hidden factors in inflation, production and stock prices cause the formation of bubbles in the stock market. Also, among the above factors, non- fundamental inflation factors is the most important factor in the formation of the stock price bubble, and then fluctuations in the production sector and the stock price itself. This results include this practical proposal that stability in the stock market and avoiding the formation of bubbles in the stock price index mainly depends on controlling the inflation rate and creating stability at the general level of prices.