FYI: For the past several years, the debate has raged in the financial industry regarding whether it is better to try to beat the markets through active portfolio management or by using low-cost index funds. While historical analysis seems to provide almost definitive evidence that the latter strategy has been more effective, the question arises as to whether indexing could become too popular, and what would happen in the markets if this were to occur. And while there are no concrete answers, the question itself is becoming increasingly relevant as a growing number of investors move their money from actively-managed instruments into passive index portfolios.
Regards,
Ted
http://www.investopedia.com/articles/investing/061616/what-point-does-indexing-get-top-heavy.asp