(Before It's News)
While ETFs have been around for nearly 25 years, they have really exploded in the past five. Exploded in terms of the assets invested in these half-stock, half-fund hybrids (more than $2.5 trillion among just U.S.-listed ETFs as of December 31, 2016, according to FactSet), the sheer number of products (nearly 2,000 listed on U.S. exchanges), and the trading volume on major markets (about 30% of daily volume in the United States during 2016, according to Credit Suisse).
Source:
http://etfdb.com/news/2017/03/20/are-investors-hurting-themselves-with-etfs/