Borsa İstanbul Bankacılık Sektöründe Sürü Davranışının Covid-19 Etkisiyle Değişimi

Abstract

Bu çalışmada, yatırımcı davranışlarını şekillendiren psikolojik eğilimlerin, finansal piyasalardaki etkisini inceleyen davranışsal finans yaklaşımı temel alınmıştır. Geleneksel finans teorilerinin, yatırımcıların tamamen rasyonel davrandığı varsayımına karşılık davranışsal finans, bireylerin zaman zaman irrasyonel eğilimler göstererek sürü davranışı sergileyebileceğini ileri sürmektedir. Bu çerçevede, Borsa İstanbul Bankacılık Endeksi kapsamında sürü davranışının varlığı, Christie ve Huang (1995) tarafından geliştirilen yatay kesit standart sapması (CSSD) ile Chang, Cheng ve Khorana (2000) tarafından önerilen yatay kesit mutlak sapması (CSAD) yöntemleri aracılığıyla analiz edilmiştir. Covid-19 öncesi dönem (01.01.2015 – 11.03.2020), pandemi dönemi (11.03.2020 – 31.12.2022) ve tüm dönem (01.01.2015 – 31.12.2022) olmak üzere üç farklı dönemi kapsayan analiz sonucunda, yalnızca pandemi sürecinde istatistiksel olarak anlamlı bir sürü davranışı gözlemlenmiştir.

Keywords

• Davranışsal Finans
• Sürü Davranışı
• Borsa İstanbul

The Impact Of COVID-19 On Herding Behavior: Borsa Istanbul’s Banking Sector

Abstract

This study investigates the impact of psychological tendencies shaping investor behavior on financial markets within the framework of behavioral finance. Unlike traditional finance theories, which assume fully rational investors, behavioral finance argues that individuals may display irrational biases and engage in herding behavior. In this study, the existence of herding in the Borsa Istanbul Banking Index is examined through the cross-sectional standard deviation (CSSD) proposed by Christie and Huang (1995) and the cross-sectional absolute deviation (CSAD) introduced by Chang, Cheng, and Khorana (2000). The analysis covers three sub-periods: the pre-Covid-19 period (January 1, 2015–March 11, 2020), the pandemic period (March 11, 2020–December 31, 2022), and the overall sample (January 1, 2015–December 31, 2022). The findings reveal that statistically significant herding behavior emerged only during the pandemic. This outcome highlights that behavioral biases and irrational collective dynamics tend to intensify under conditions of heightened uncertainty and market stress. By simultaneously employing both CSSD and CSAD measures and systematically testing period-specific heterogeneity, this study provides empirical evidence that enriches the behavioral finance literature in the context of the BIST Banking Index.

Keywords

• Behavioral Finance
• Herding Behavior
• Borsa Istanbul

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