Related: U.S. ETF Investors Shy Away from Domestic Markets

Second quarter ETF flows also showed robust investment demand for four asset categories, including international equity, U.S. fixed income, U.S. equity and sector plays.

Charles Schwab offers a line of various ETFs that have grown popular for their cheap costs and commission-free trades on the Schwab OneSource platform, including the Schwab International Equity ETF (NYSEArca: SCHF), Schwab U.S. Aggregate Bond ETF (NYSEArca: SCHZ) and Schwab U.S. Broad Market ETF (NYSEArca: SCHB), among others.

Charles Schwab offers 21 ETFs with $81.1 billion in assets under management, and they come with an average 0.12% expense ratio. The issuer offers some of the cheapest ETF plays in the industry, with SCHB coming in at a dirt cheap 0.03% expense ratio.

For more information on the ETF industry, visit our ETF performance reports category.