Because commodity prices help determine Canada’s terms of trade, employment, income and, ultimately, inflation, it is important to understand what causes them to fluctuate. Since the early 1900s, there have been four commodity price supercycles—which we define as extended periods of boom and bust that can take decades to complete. Now in its downswing phase, the current supercycle started after growth in China and other emerging-market economies in the mid-1990s resulted in an unexpected demand shock. The extent of this downswing depends on numerous factors that are presently uncertain.