The Vanguard S&P 500 ETF (VOO.P), opens new tab, the index investing pioneer’s flagship exchange-traded ​product, became the first in the history of ‌ETFs to reach and exceed $1 trillion in assets, the investment firm confirmed.

The Vanguard fund hit this milestone, ​the latest record in the remarkable ascent ​of exchange-traded funds, less than 18 ⁠months after overtaking State Street Investment Management’s SPDR ​S&P 500 ETF (SPY.P), opens new tab in assets, as investors looking for ​broad market exposure also sought out the lowest-cost funds. VOO levies a management fee of only 0.03%, compared to 0.09% ​for the State Street fund, which now is ​third in the three-way race between those two firms and ‌BlackRock ⁠Inc. (BLK.N), opens new tab.

BlackRock, the world’s largest asset manager, has the second-largest ETF tracking the Standard & Poor’s 500 index, with its iShares Core S&P 500 ETF (IVV.P), opens new tab that now boasts $860 ​billion in ​assets and ⁠fees of 0.03%, according to VettaFi. SPY, the market pioneer that helped open ​up the ETF market with its 1993 ​launch, ⁠now has $785 billion in assets.

“This is a key milestone,” said Todd Rosenbluth, head of research at VettaFi. “Investors continue ⁠to ​turn to low-cost broad market ​exposure to gain access to the S&P 500 using VOO.”