The exchange traded fund universe continues to expand as Charles Schwab data reveals increased demand for the cheap and efficient investment tool across all investor segments, along with rising appetite for low-cost Schwab products.

According to a recent Charles Schwab research note of clients on the Charles Schwab platform, ETF assets at Schwab increased 29% to $355 billion at the end of June from $276 billion in June 2016. Looking at the various investment groups, retail traders saw a 34% rise in demand for ETFs, retail investors experienced a 25% increase in demand for ETFs and RIA clients exhibited a 30% leap in demand.

Meanwhile, second quarter ETF flows were $12 billion, contributing to 12-month flows through June 2017 of $43 billion, or up 61% compared to the prior 12-month period.

RIA clients accounted for 51% of ETF flows in the past 12 months, compared to 53% in the same period last year. Retail investors decreased their share slightly from 41% last year to 40% this year while retail traders saw their share rise from 6% to 9%.

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.