Investors poured almost $1 billion into Fidelity Investments' two zero-fee index funds in their first month of operation.
The Fidelity Zero Total Market Index Fund attracted $753.5 million through Aug. 31, while the Fidelity Zero International Index Fund gathered $234.2 million, according to Fidelity's website.
"A billion in a month is a great showing when you consider that the funds are available only to retail investors," said Ben Johnson, head of global ETF research at Morningstar Inc.
Johnson pointed out that bigger, established funds routinely take in more money each month. In July, for example, Vanguard's Total International Stock Index Fund attracted $4.8 billion, according to Morningstar data.