 As of November 2010 a commodity ETF, namely SPDR Gold Shares, was the second-largest ETF by market capitalization.Generally, commodity ETFs are index funds tracking non-security indices.Because they do not invest in securities, commodity ETFs are not regulated as investment companies under the Investment Company Act of 1940 in the United States, although their public offering is subject to SEC review and they need an SEC no-action letter under the Securities Exchange Act of 1934.