Warnings that index funds have broken the stock market all imply a threshold: a share of the market at which price discovery fails. Nobody making the argument names it. Owen Lamont, writing in the Financial Analysts Journal, argues that no such number exists short of complete passive ownership, and that what actually determines whether prices stay informative is who is left doing the trading. His case, the strongest peer-reviewed research against it, and what the performance
Fifty years ago this week, the first index fund for ordinary investors went on sale and almost nobody bought it. The company behind it had been named two years earlier after a ship in a picture on its founder's wall. The story Vanguard tells about its own beginnings is tidier than what actually happened, and less useful.
