Vanguard Group's Extended Market Index Fund will change its target benchmark from the existing Dow Jones Wilshire 4500 to the Standard & Poor's Completion Index.
The switch, which will affect all four of the $9 billion fund's share classes, "will complement the Vanguard 500 Index Fund," the company's $102 billion fund, which has tracked the S&P 500 since 1976, said Gus Sauter, chief investment officer.
The S&P Completion Index represents mid- and small-capitalization stocks and was developed by Standard & Poor's to complement the large-capitalization S&P 500 Index.
"By holding a combination of the two Vanguard index funds, investors may obtain exposure to the entire U.S. stock market," Sauter said.
The change to the new S&P benchmark is expected to occur between May 31 and December 31, 2005, and will not affect the fund's investment objective or strategy, Vanguard said.