Nurul Latifatul Inayati

This research paper aims to explore the market efficiency of stock exchanges in of ASEAN-5 countries, Indonesia, Malaysia, Singapore, Thailand, and the Philippines, during the COVID-19 pandemic. Stock market efficiency is the degree to which stock prices reflect all available relevant information. In an efficient market, stock prices will immediately rise or fall to reflect new information released by a company. This study uses the Stochastic Frontier Analysis (SFA) method to determine the efficient value over time. Market efficiency generally refers to how well financial markets in these selected countries reflect all available information, particularly in the context of the COVID-19 pandemic. SFA is useful here as it can separate random errors from inefficiencies, allowing us to isolate the impact of COVID-19 on market efficiency levels across these countries. The results show that the stock markets of ASEAN-5 countries (Indonesia, Malaysia, Thailand, Singapore, and Philippines) are efficient during the COVID-19 pandemic. Based on the hypothesis test, for the overall period of 2021 and 2023, the average efficiency ranges from 0.68 to 0.72, and for the time period/per year the average efficiency ranges from 0.66 to 0.74. The efficiency of the Philippine stock market based on time period/per year shows the average maximum efficiency in 2021 (0.74) and 2023 (0.73). While the average efficiency of the Malaysian stock market shows the minimum level of efficiency in 2020 (0.66) and 2021 (0.68).

Acknowledgment
The authors would like to thank the Research and Innovation Institute (LRI), Universitas Muhammadiyah Surakarta, for the enormous financial support in writing this study.