Seven of the nine ETCs track the performance of sub-indices of the S&P GSCI Total Return Index. These indices track the performance of agricultural products and commodities, grains, livestock, industrial metals, precious metals and the energy sector. Investors can also track the performance of the commodities index S&P GSCI Total Return with the iPath S&P GSCI Total Return ETN. The index comprises agricultural products, energy, livestock, and industrial and precious metals.