New Delhi, May 27 -- Throughout my teaching and writing over the decades, I have tried to universalize the idea that using low-cost index funds that buy and hold all the stocks of companies in the market is the optimal method of investing. Over 10- and 20-year periods, that investment strategy produces higher returns than more than 90% of the portfolios that are actively managed by professional investors. It is easy to implement and accessible to anyone and everyone.

I have frequently demonstrated the benefit of index investing by calculating the theoretical returns of a "John Doe" investor who put an initial $500 into the first index fund that began in January 1978 and then $100 each month thereafter. The final value of that investment,...