Fundamental economic factors—market demand and supply conditions—provide the most consistent explanation for trends in commodity prices from 2004 to 2011. This paper presents empirical evidence that the rise and fall of commodity prices on a monthly basis can be strongly linked to the value of the U.S. dollar and the world business cycle—in particular, to the strength or weakness in emerging market economies such as China, Brazil, India, and Russia. Despite concerns raised by some policymakers that increased commodity index investment (the financialization of commodities) has driven commodity price movements, numerous academic studies have concluded that index-based investing has not moved prices or exacerbated volatility in commodity markets in recent years. An examination of weekly and monthly net flows into commodity mutual funds reveals that these flows have little or no effect on the overall growth rate of commodity prices. In particular, weekly flows into commodity mutual funds do not lead to future commodity price changes. These results are consistent with academic papers that find little or no impact of commodity index investors on commodity prices in individual markets. The paper concludes by briefly discussing three key factors that illustrate why flows into commodity mutual funds cannot explain commodity price movements.