As the amount of money invested in commodity indexes (like mutual funds, but of commodities instead of stocks and bonds) increase dramatically so too did the price of commodities. Commodity indexes are like mutual funds made of commodity futures, where people buy and hold commodity futures for long periods of time, as they would with a piece of stock in a company.
DJ-AIG = Dow Jones-AIG commodity index
SP-GSCI = Standard & Poors-Goldman Sachs commodity index
As index speculators poured money into the commodity futures markets, it drove up commodity prices. Here you see the price going up while the percentage of investments from outside index speculators grew. These speculative inflows created a bubble in commodity prices.