On the commodity side, indexes have existed for decades but it wasn't until the beginning of the most recent commodity bull market that funds were established to track the performance of the various commodity indexes. The idea of investing in commodities has come a long way since the pioneering days of commodity trading advisors John W. Henry, Bill Dunn and Keith Campbell. Today, money benchmarked to commodity indexes is estimated to be between $185 and $260 billion. There also are several commodity ETFs based on certain indexes. Three ETFs are based on one of the Dow Jones AIG Commodity Indexes and several are based on the S&P GSCI. ETFs allow investors to benchmark performance to a particular index without paying the added cost of an active manager. Commodity ETFs in general are not responsible for physical delivery.