Exchange-traded funds received record amounts of fresh cash last month to push their total value past the $4 trillion market globally, the latest data show.

A record $37.94 billion was pumped into ETFs in April, the 39^th straight month of net inflows, according to a Financial Times report that cites data from ETFGI. Investor appetite for low-cost passive asset management that puts money into a broad range of securities shows no sign of slowing.

The money going into passive investments is hurting active fund managers that are more selective about the stocks and bonds they trade. Investors are shunning active funds that charge high fees for lackluster performance.

“The active asset management headwinds aren’t abating,” Ben Johnson, head of ETF research at Morningstarm told the FT. “It’s not about performance any more. It’s structural.”

There are now about 7,000 exchange-traded products managed by 313 providers, ETFGI data show. BlackRock’s iShares had the most net inflows last month at $23.9 billion, followed by Vanguard’s $10.29 billion and Schwab’s $2.53 billion.

Only about two-thirds of “large-cap” fund managers that put money into high-quality U.S. stocks managed to beat their benchmarks in April, which was the highest outperformance in more than two years, according to Bank of America Merrill Lynch.

The shift to ETFs will pressure revenue at asset-management firms, according to a report by Morgan Stanley and Oliver Wyman that was published in March.

If the economy doesn’t grow or asset prices decline, investment manager sales might fall by about 30 percent, they said.

“Sustained fee pressure is a growing threat for asset managers,” Morgan Stanley’s analysts wrote. “The correlation between fund performance and flows has weakened, with fee levels becoming the more important driver.”

• Morgan Stanley: Asset Manager Revenue May Fall 30 Percent by 2019
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