Karl Marx hypothesized that there is a long-term tendency for the profit rate to fall in capitalist economies. Immanuel Wallerstein hypothesized that capitalist development tends to drive up labor cost, material cost, and taxation cost. This book evaluates Marx's and Wallerstein's hypotheses by studying the long-term movement of the profit rate and contributing factors in major capitalist economies. During the twentieth century, leading capitalist economies largely succeeded in stabilizing the profit rate. However, the current decline of the profit rate in China may precipitate the global capitalist economy into a new major crisis. As economic growth slows down in all major capitalist economies, Marx's original hypothesis may be verified by the global economic events in the twenty-first century.