What is the difference between an ETF index and other indices? S&P Index: "The S&P 500, or the Standard & Poor's 500, is a stock market index based on the market capitalizations of 500 large companies having common stock listed on the NYSE or NASDAQ. The S&P 500 index components and their weightings are determined by S&P Dow Jones Indices. It is one of the most commonly followed equity indices, and many consider it one of the best representations of the U.S. stock market, and a bellwether for the U.S. economy." ------- VOO is an S&P 500 ETF by Vanguard. Stocks included in S&P 500 index are determined and maintained by S&P. If US economy is doing well, then should VOO. Other ETF relies on the stock selection by the offered company. Some ETF picks large companies in a sector, some picks all companies in a sector, etc. Based on the current market, I think ETFs for financial sector and mining sector are at bargain prices, and should do well in the medium term. Financial/bank sector is the backbone of the economy, but currently they are not out of legacy issues or completely complied to new (future) rules --> they're adjusting their business to comply to those. Selected financial ETF should be doing well. Mining sector is in trouble with low prices on base metals, because the economies of many major economies are not recovered completely. Selected ETF for mining sector should be doing well in medium term, too. US housing market have been recovered ---> does not look like we can find bargain prices in housing related equities --> does not mean that those real estate equities will not do well in the future.