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China and the United States are in the grip of major structural changes that both dread will end the Halcyon era when China produced low-cost goods and the US bought them. In particular, many fear that if these changes lead to direct competition between the two countries, only one side can win.

That fear is understandable, but the premise is mistaken. Both sides can and should gain from forging a new relationship that reflects evolving structural realities: China’s growth and size relative to the US; rapid technological change, which automates processes and displaces jobs; and the evolution of global supply chains, driven by developing countries’ rising incomes. But first they must acknowledge that the old pattern of mutually beneficial interdependence really has run its...