University of TehranFinancial Research Journal1024-815392320070522evaluating the stability of systematic risk in Tehran stock exchangeevaluating the stability of systematic risk in Tehran stock exchange27211FAJournal Article19700101This study aims at testing the degree of stability for beta coefficient across time, depending on the information available from Tehran bourse. Where beta coefficient was calculated using the market model developed by Sharp on 1963, which applies by performing a simple linear regression between the company’s and the market returns, where beta coefficient is the slope of this regression. In this study we examine the stability of beta by using the structural change methodology of the chow testThis study aims at testing the degree of stability for beta coefficient across time, depending on the information available from Tehran bourse. Where beta coefficient was calculated using the market model developed by Sharp on 1963, which applies by performing a simple linear regression between the company’s and the market returns, where beta coefficient is the slope of this regression. In this study we examine the stability of beta by using the structural change methodology of the chow testhttps://jfr.ut.ac.ir/article_27211_14a1da20f55df8851c83a9860a104f19.pdf