As markets continued to rise in April, assets held in exchange-traded funds increased for the third consecutive month.

According to monthly data from State Street Global Advisors released Monday, assets held in U.S. ETFs rose 2.9% from a month earlier to $830 billion. ETFs outpaced the Standard & Poor's 500 Composite Index, which rose 1.5% in April.

Gains were evenly distributed across all 12 ETF categories, with six gaining more than $2 billion in assets. Small-cap ETFs had the largest gain, climbing $2.7 billion, followed by mid-cap ETFs, which gained $1.7 billion.

As of April 30, there were 888 ETFs managed by 31 investment managers nationally.

The top three ETF managers collective accounted for 84% of the U.S. listed ETF assets, down 0.3 percentage points since the end of last year. BlackRock, which bought the iShares family of funds from Barclays, managed 47.7% of assets, State Street had 22.9% share, and Vanguard 13.1%.

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