Abstract China's rise, Russia's military resurgence, and India's economic growth have prompted debates about the end of unipolarity and the future balance of power. Such debates are a staple of international politics; indeed, in the late twentieth century, many observers warned that Japan and the Soviet Union would overtake the United States. Yet scholars and policymakers evince little agreement on how to define power or measure the distribution of power. This article introduces an inductive method for comparing national power. I empirically validate common metrics of national capabilities—economic and military—by assessing their ability to both predict known balances of power across historical systems (1820–1990) and distinguish between great powers and other countries. This method yields three important findings. First, large gaps in national capabilities between great powers and even superpowers have been common throughout history. Great powers need not achieve parity with the leading state to engage in a dangerous security competition. Second, this method shows that China on most dimensions is not only a great power but a superpower. Third, neither Russia nor India is a great power. The system is bipolar. These findings inform debates about the stability of international politics and the future of international order and suggest the likelihood of shifts in U.S. grand strategy and alliances.
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