Do psychological factors exert greater influence on investment decisions than physiological factors? Evidence from Borsa Istanbul

Abstract

We investigate the impact of Ramadan, the Holy month of fasting, on the phenomenon of post-earnings announcement drift (PEAD) in Borsa Istanbul. Utilizing quarterly earnings announcements and employing both the analyst forecast method and time series forecast method as surprise measures, our study spans the earnings period from the first quarter of 2007 to the last quarter of 2018. Our objective is to bridge the gap between studies highlighting the negative impacts of physiological factors and the positive impacts of psychological factors on economic decision-making. Given the anticipated opposing effects of physiological and psychological factors on PEAD during Ramadan, our findings offer a unique opportunity to compare the influences of physiology and psychology on investment decisions. Contrary to the expected positive impact resulting from physiological factors causing attention deficit, our research reveals that earnings announcements made during Ramadan exhibit, on average, a 16–25% lower drift in the subsequent 60-day period, depending on the method used. We attribute this unexpected outcome to the dominance of psychological factors, such as heightened sentiment, self-awareness, and spirituality, over physiological factors. This finding holds significance for policymakers, as activities that may seem to have a harmful impact on the economy due to visible physiological or physical factors can unexpectedly yield positive effects due to less tangible psychological factors. Additionally, our results hold importance for investors, as a hedge strategy using earnings surprises results in a negative return if the announcements are made during Ramadan. Our findings remain robust across different measures of PEAD and various intensities of physiological factors.