Resumen
The Efficient Market Hypothesis, developed by Fama, is a market in which prices reflect the current information and where abnormal returns are not possible. In case the securities value reflects the information fully, the existence of the efficient market is mentioned. Within the framework of market mechanism, if these concepts are not sufficient, behavioral finance has emerged focusing on the effect on stock prices. A brand is a symbol, a name or a combination of a merchandise for distinguishing it from the like.Owning a brand is more than a logo or symbol.The brand covers the entire business and affects the perception of customers. Brand value is the value of the brand's name, symbol and reputation.. Thus, the arrangements within the company that can be useful within the company could be done in a timely manner. Creating a brand and brand value has been a powerful competitive tool for businesses.Brand Finance, covers Turkey's most valuable 100 brands. To measure the strength and value of these brands, it annually determines the value of the world's largest brands and publishes its ranking. In this research, the effects of the increase, decrease and constant brand power on the share prices of companies listed in the BIST 100 index in the list of Brand Finance Turkey 100 in the years 2012-2017 were analyzed. According to the findings, it is seen that the changes in brand ranking have an effect on market performance of firms.