Second-to-market Vanguard Total Bond Market ETF (NYSEArca: BND) surpassed the iShares Barclays U.S. Aggregate Bond ETF (NYSEArca: AGG) in assets last Thursday, largely because it costs investors half as much, according to Forbes.

AGG launched September 2003, amassing $6 billion in assets by the time BND launched in April 2007, Forbes says.

Both ETFs track the Barclays Capital Aggregate Bond Market Index. However, it’s clear investors favor BND for its lower expense ratio—0.11 percent compared with 0.22, respectively—which happens to deliver higher returns as well.

For the full story, head over to Forbes.com.