I agree we're not to over indexing in the US, but I think people really have to keep watching the central banks, especially Japan and the BOJ [1]. While the US

I agree we're not to over indexing in the US, but I think people really have to keep watching the central banks, especially Japan and the BOJ [1]. While the US federal reserve doesn't buy stocks, other central banks do, and a lot of them use indexing/ETFs. The swiss national bank also has a fair amount of US stock holdings.[2] Given how the central banks act, this affects the currency markets and interest rates. (1) https://asia.nikkei.com/Markets/Equities/Japan-s-central-bank-nearly-doubles-ETF-holdings-in-one-year https://asia.nikkei.com/Markets/Equities/Japan-s-central-ban... (2) http://www.businessinsider.com/swiss-national-bank-owns-80-billion-us-stocks-2017-6 http://www.businessinsider.com/swiss-national-bank-owns-80-b...