A Vanguard Group equity fund has become the first of its kind to eclipse $1 trillion of assets, a testament to the rise of index-based investing over the past three decades.

Vanguard Total Stock Market Index Fund, which includes both a mutual fund and an exchange-traded fund, had $1.04 trillion of assets as of Nov. 30, company data show.

“Given that Vanguard birthed index investing, it seems only fitting that one of their flagship funds would be the first to reach this historic mark,” said Nate Geraci, president of the ETF Store, an investment advisory firm.

While soaring U.S. stocks are fueling the fund, it’s also being bolstered by falling fees, a trend stoked by Vanguard, a pioneer in low-cost passive investing. The Vanguard Total Stock Market Index Fund was created in 1992, with the corresponding ETF following in 2001.

“Investors have become much more educated on the importance of fund fees and the serial underperformance of active management,” Geraci said. Those factors could further propel the fund for decades, he said.

Vanguard follows an unusual format, with its ETFs existing as a share class of its mutual funds. The Vanguard Total Stock Market ETF attracted the most cash of any ETF so far this year, with $30.8 billion of net inflows. Vanguard, the top issuer for ETF inflows this year, controls 28% of the $5.3 trillion U.S. ETF industry.

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