A monopoly obtains when one firm is free to set prices and output while keeping ambitious newcomers out of the market. The best example is Standard Oil in the late 19^th century. Ruthlessly undercutting competitors, the company ended up controlling 90 percent of refined oil flows in the United States. The United States never had that kind of overweening power in the international “market.” It may have come close to unipolarity in the 1990s when its mortal rival, the Soviet Union, had committed suicide. Yet the contemporary world is no longer unipolar. Neither is it bi- or multipolar.

By traditional measures—military strength, economic wealth, population size—the United States remains the world’s preeminent superpower. Its economy continues to expand; it deploys the largest military in the world; it is home to a growing population; and American laws and capital flows encourage a vibrant ecosystem for innovation.