The good news: I don’t think Donald Trump will cause a global trade war.

The bad news: The reason I say that is I believe that a trade war would be coming even if Trump had lost the election, largely because China is refusing to act like a responsible economic superpower. Unfortunately, Trump may be the worst possible person to guide U.S. policy through the turmoil that’s probably ahead.

He won’t be the reason we have a trade war, but he may well be the reason we lose it.

China is the greatest economic success story in history. It used to be very poor; there are still many people alive who remember the great famine of 1959-61. But after the reforms that began in 1978 its economy soared. Even now, China is only a middle-income country, with G.D.P. per capita substantially lower than ours or in Western Europe. But China has a huge population, so by some measures it is now the world’s largest economy.

However, all indications are that China’s era of torrid economic growth is behind it. For decades, Chinese growth was fueled mainly by two things: a rising working-age population and rapid productivity growth driven by borrowed technology. But the working-age population peaked around a decade ago and is now falling. And despite some impressive achievements, the overall rate of technological progress in China, which economists measure by looking at “total factor productivity,” appears to have slowed to a crawl.