Month of Ramadan effect swings and market becomes adaptive
Authors: Shahid Muhammad Naeem , Sattar Abdul , Aftab Faisal , Saeed Ali , Abbas Aamir 
Published: May 2019

Purpose
This paper aims to enhance the existing literature on adaptive market hypothesis (AMH) as this study first time links the month of Ramadan with AMH that permits the performance of well-known Ramadan effect to fluctuate over time.

Design/methodology/approach
To fulfill the purpose, the authors inspect the daily returns of 107 individual firms listed at Pakistan Stock Exchange over the period of 20 years. To explore the varying degree of return predictability during Ramadan, the authors use four different subsamples comprising equal length of observations of five years each. The authors use a GARCH (1,1) regression model which facilitates for time varying nature of volatility in equity returns. To facilitate the non-normal nature of stock return data, the authors use Kruskal–Wallis test statistic.

Findings
The authors find that behavior of Ramadan effect evolves over time, as performance of this effect varies from time to time and consistent with AMH. Finally, the paper proposes that AMH is well elucidation of behavior of Ramadan effect than traditional efficient market hypothesis.

Research limitations/implications
First limitation is related to the choice of sub-sample as the study uses a sub-sample of five years. Second, the authors ignore transection cost (commissions, fee and taxes) as it is freely negotiated and varies between 4 and 10% (Khan, 2013). Due to such varying information we ignore the transaction cost. It is suggested that a sub-sample analysis of long period may be a more appropriate method to elucidate the idea of AMH in future research and suggest the current method could be adapted and helpful to examine other calendar and market anomalies in different equity markets.

Practical implications
The paper includes implications for investors to choose a better model for investment. Investors can exploit greater returns in future month of Ramadan periods. Furthermore, the researchers can easily extend the methodology used in the study to address multiple issues like adaptive behavior of returns from bonds, real estate investment trusts, cryptocurrencies and trading rules of strategies.

Social implications
Study confirms from sample t-test and GARCH (1,1) model that Ramadan effect is present in the full and in certain sub-samples; therefore, based on these discrepancies investors can earn abnormal returns by developing specific investment strategies as investors usually make investments in share according to the religious context of Islamic Calendar. The results provide good references for suitable time of investment in stock market. The findings of this study will be helpful to investors and brokers as well as portfolio managers to capture favorable returns across the Islamic calendar.

Originality/value
The paper identified need to study why behavior of Ramadan effect varies over time. The data set comprises daily returns of 107 individual companies over the period of 20 years to better investigate the varying nature of anomalous effect of month of Ramadan. The findings are valuable for international investors and portfolio managers.