Behavioral finance and an application in Istanbul Stock Exchange

Ekonomi ve finans alamndaki teorilerin onemli. .bir kisrru piyasalann etkin oldugu ve bireylerin yatmm yaparken mevcut bilgiyi rasyonel sekilde degerlendirdikleri varsayimma dayanmaktadir. Bununla beraber gunluk hayatta karar verici konumundaki bireylerin rasyonel olmayan davranislar sergiledikleri ve tekrar eden yargilama hatalarma dustukleri yapilan bircok deneysel calisma ile ortaya konmustur, Ozellikle l 980'1i yillardan itibaren finansal olaylan aciklama konusunda geleneksel teorilerin yeterliligi tartisihr hale gelmistir, Kahneman ve Tversky (1979)'nin cahsmalan neticesinde literature giren davramssal finans, bireylerin bu rasyonel olmayan davramslannm sebeplerini, yatmm kararlanna etkilerini ve sonuclanm kendisine inceleme alam yaprmstir. Cahsmamn birinci bolumunde geleneksel teoriler ve Kahneman Tversky'nin l Beklenti Teorisi'nden bahsedilmistir. Ikinci bolumde rasyonellikten uzaklasmaya sebep olan asm guven, iyimserlik, belirsizlikten kacmma, pismanhktan kacmma, I ..l : hevristikler, bilissel celiski, asm tepki ve dusuk tepki gibi bircok yatinmci egilimi detayh olarak aciklanmisnr. Son boltimde ise, farkli i.ilkelerde gecerliligi test edilmis olan asm tepki hipotezinin Borsa Istanbul'da 2010-2018 doneminde gecerli olup.olmadigma yonelik bir arastirma yapilmistrr. De Bandt ve Thaler (1985) yonteminden yararlamlarak yapilan calisma neticesinde asm tepki hipotezini destekler nitelikle ve istatiksel olarak anlamh sonuclar elde edilmistirA significant portion of the theories in economics arid finance are based on the assumption that markets are efficient and that individuals are rationalizing the current knowledge when investing. However, in daily life, the decision-making position of individuals exhibited irrational behavior and repeated trial errors have been revealed by many experimental studies. In particular, the adequacy of traditional theories has become debatable in explaining,, fin.a:ncil events since the 1980s. As a result of the studies of Kahneman and Tversky .(1979), behavioral finance, which entered into the literature, investigated the causes, effects and consequences of these irrational behaviors of individuals on investment decisions. In the first part of the study, traditional theorie and Kahneman Tversky's expectation theory were mentioned. In the second part;_ many ;fovestor tendencies such as overconfidence, optimism, uncertainty avoidance, avoidance of repentance, heuristics, cognitive dissonance, overreaction and low; reaction are explained in detail. In the last section, a survey was carried out to , determine whether the overreaction hypothesis, which has been validated in different countries, is valid in the stock market in 2010-2018. As a result of the study using De Bondt and Thaler (1985) method, it supports the excessive reaction hypothesis and statistically significant results were obtained