For State Street Corp. , the company that pioneered the $5 trillion exchange-traded fund industry, it’s been a long way down.

Earlier this month, the Boston firm’s asset-management division reported that investors took out as much cash as they put into its $639 billion ETF business this spring. It was the worst showing among the three largest issuers and sent State Street Global Advisors’ share of the U.S. ETF industry to an all-time low.

State Street launched the first ETF 25 years ago and dominated the market for a decade. Today, its slice of U.S. ETF assets is just 17.3%—down from 49% 15 years ago. More worrying for its future, State Street captured just 5.9% of the $343 billion that poured into ETFs in the past year. By contrast, Vanguard Group and BlackRock Inc.’s iShares took in a combined 67%. Even Charles Schwab Corp. , a relative newcomer with just 22 ETFs, had a fatter haul.

How State Street squandered its first-mover advantage for one of the most popular financial products ever created shows that being first can sometimes be as much of a hindrance as a head start.

It’s easy to point out State Street’s missteps in hindsight, but no one knew then how big the ETF industry was going to be, said Jim Ross, chairman of State Street’s global SPDR business. “If you go back 25 years, you can think of some things you might do differently,” he said.