XOP offers an equal-weighted approach to oil and gas exploration and production. Based on the GICS classification, the fund provides exposure to the oil and gas exploration and production segment of the S&P Total Market Index, the parent index, which includes Integrated Oil & Gas, Oil & Gas Exploration & Production, and Oil & Gas Refining & Marketing. Equal weighting provides diversified exposure to an industry normally dominated by a few big names, but also produces a bias to small- and midcaps. The index is reviewed and rebalanced quarterly.