In This Research, We Studied The Application of Downside Capital Asset Pricing Model in Tehran Securities Market. At First, & Downside ( ) Coefficient have been Estimated & Then they have been Compared with Each Other by SAS 9. Soft ware. At The Second Stage The CAPM & D-CAPM Models Were Compared And Finally The Efficiency of Two Model's Portfolios Were Tested. Research's Result Shows That Downside is Better Estimation Than and Also D-CAPM is Better Model than CAPM for Showing Relation between Risk & Return.
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