As the index fund turns 40 years old this week, the same question remains, “Will the growth of index funds and passive investment management become too large?”

We get this question a lot from folks who worry about the growing success of index funds. The Wall Street Journal discusses the complex thought and some concerns surrounding the passive investment movement. Index fund pioneer John Bogle, doesn’t rule out the idea that passive investing could become too large. However, he explains that the rise of index funds would require much greater growth than already seen by economists. The market would need to see at least 90% of investments in index funds. Jason Zweig explains the reasoning for an active investing presence and shares data on why active management is unlikely to vanish anytime soon. Happy Birthday Index Fund!