Vanguard's move was seen by analysts as a potential game-changer for the U.S. actively managed funds industry that would increase competition and push down costs.
ETF buyers are building their holdings, joining hedge funds that have boosted their net-long position in bullion futures by almost nine-fold since early July.
The S&P 500 Financial Index fell 2.2 percent on Tuesday, the most since May, compared with a 0.8 percent decline in the full index, the widest gap in five months.
Northern Trust's FlexShares pioneered multifactor ETFs with the U.S. Market Tilt Index Fund in 2011. FlexShares' Shundrawn Thomas on the appeal of multifactor strategies, and the risks.