The impact of the Covid-19 crisis on the efficiency of the US stock market

Abstract

This paper search the impact of COVID-19 on the efficiency of financial markets, Specifically, the impact of Covid -19 on the Standard and Poor’s 500 (S&P500) index, using three efficiency indicators: Run test, Ljung-Box test, and Bartels test, We used daily data for return (S&P500) index, from 2-10-2019 to 30-06-2020, Divided into two periods, the pre-crisis period from 2-10-2019 to 10-3-2020, and the crisis period from 11-3-2020 to 30-6-2020, the results suggest that the return appeared to be more volatile during the (COVID-19)crisis period and the U.S stock market(s&p500) was efficient in weak form during pre-crisis COVID-19, and not efficient during crisis COVID-19 After the world organization announced that the Coronavirus is a global epidemic.