Equity portfolio diversification: how many stocks are enough? evidence from India

Abstract

How many stocks are required to reduce unsystematic risk significantly is an important question for investors. While there is a large body of research on the subject in the United States, there is little formal work on this question in India. We show that a 15-20 stock portfolio, the traditional market rule-of-thumb for a diversified portfolio, is likely inadequate to minimise unsystematic risk. We show that an investor could target to reduce diversifiable risk by 90% with a 90% confidence with a portfolio of 40-50 stocks. We build a practical framework that serves as a baseline for investors to target a specific reduction in diversifiable unsystematic risk at a chosen confidence level.