As major market indices continued to buoy, exchange-traded-fund assets under management rosein March.

According to monthly data from State Street Global Advisors (STT) released last week, assets held in U.S. exchange-traded funds rose 7.2% from a month earlier to $806 billion. For the month, ETFs outpaced the Standard & Poor’s 500 Index, which rose 6% last month.

Ten of 12 ETF categories rose in March, according to State Street. The size and international categories accounted for 57% of the $54 billion gained overall in March.

As of March 31, there were 863 exchange-traded funds in the United States managed by 31 companies nationally.

The top three ETF managers collective accounted for 84% of the U.S. listed ETF assets, up 0.2 percentage points from a month earlier. BlackRock [BLK], which bought the iShares family of funds from Barclays, managed 47.8% of assets, State Street had 23.3% share, and Vanguard 12.9%.

Despite this overwhelming majority, other large companies are entering the ETF space. Last month, JPMorgan Chase & Co. [JPM] announced in a pair of filings with the Securities and Exchange Commission that it plans to introduce a pair of exchange-traded funds.

The New York company said it plans to introduce both actively managed and index-based ETFs. It plans to launch its first actively-managed ETF later this year that would invest in about 300 domestic large-cap stocks. For such actively managed ETFs, JPMorgan Chase wants to be able to have funds that can hold stocks, bonds, open end funds, closed end funds and unit investment trusts.

The company is also interested in a pair of index-based ETFs. They want one that tracks an index of investment-grade U.S. municipal bonds with maturities between one and 12 years, and another that will track investment-grade U.S. corporate debt with an issuance of at least $300 million.