Natural resources power rankings are rankings between U.S.-listed natural resource ETFs on certain investment-related metrics, including 3-month fund flows, 3-month return, AUM, average ETF expenses and average dividend yields. The metric calculations are based on U.S.-listed ETFs that are classified by ETF Database as being mostly exposed to a specific natural resource. If an ETF changes its natural resource classification, it will also be reflected in the investment metric calculations. The calculations exclude inverse ETFs.