The Effect of Interbank Interest Rate on Stock Price (With emphasis on Joint Comprehensive Plan of Action)

Stock market developments affect the economic real sector. Banks are one of the sources of demand in the stock market. The banks investment in stock market depends to various factors. In this paper, the effect of interbank interest rate on stock index in the framework of Autoregressive Conditional Heteroscedasticity models (ARCH and GARCH) using monthly data in Iran's economy in the period from March 2013 to March 2016 has been studied. The results of the estimation of the specified models indicate that firstly, the real interest rate of interbank has a negative and significant effect on the stock index; so that the positive changes in the real interbank interest rate encourage banks to invest their additional resources in the stock market which reduces shares demand by banks and has the negative effect on stock price index. The inverse relationship between changing interbank rate and stock index confirms the importance role interbank market in monetary policy by central bank. Secondly, informal exchange rate changes have a negative and significant effect on the stock index, while the increase in the informal exchange rate, by the encouragement of exchange demand, has a contraction effect on the stock market and decreases the stock index. Thirdly, The Joint Comprehensive Plan of Action as a good news for the market has been considered and has had a positive and significant impact on the stock price index during the period under review. This finding confirms the effect of political factors on stock market changes.