The first exchange-traded fund was born 25 years ago this week, enabling investors for the first time to buy or sell the S&P 500 index in a single publicly traded share. Over the years since then, ETFs have come to dominate the financial landscape.

Today, there are almost 7,200 exchange-traded products world-wide with $4.8 trillion in assets, according to London-based research firm ETFGI. Growth is accelerating as investors forsake active money managers in favor of passive, index-tracking funds. Last year, U.S. ETFs raked in a record $466 billion, a 61% increase over 2016 inflows, according to Morningstar Inc.

Originally conceived as a trading tool for sophisticated institutional investors, ETFs have evolved into a democratizing force, lowering costs and giving retail investors access to trading strategies once available only to professionals.

The fast-growing market has also been blamed for inflating asset prices and exacerbating price swings in markets ranging from gold mining stocks to oil futures. ETFs notoriously contributed to haywire trading on Aug. 24, 2015, when mismatches between ETF prices and their underlying stocks snarled markets for hours.

“I tend to think the good has outweighed the bad, but there’s no question that there have been growing pains in the ETF market,” said Christian Magoon, an industry veteran and chief executive officer of Amplify ETFs.