5 Ways ‘Passive’ Investing Is Actually Quite Active - Bloomberg

https://www.bloomberg.com/view/articles/2017-03-03/5-ways-passive-investing-is-actually-quite-active

1. Index Construction
2. Portfolio Management   You can tell how well passive managers play this game by using an underrated metric called “tracking difference,” which basically measures how far off an index fund or ETF is from its index’s return. 
3. Usage in Portfolios
4. Engagement With Companies
Right now, index funds and ETFs via Vanguard and BlackRock own 12 percent of the stock market. (This number is expected to grow quickly, with 75 cents of every new dollar invested in the U.S. going into these two companies’ index-based products.) 
5. Above-Average Returns