China’s growth has also slowed, but much of the downturn can’t be credited to U.S. trade actions. Instead, the slowdown largely reflects the limits of Beijing’s tendency to prop up growth through short-term investment and state-owned enterprises, even as its demography worsens and productivity growth slows.

Market movements have also blunted some of the impact that tariffs might have had, reducing U.S. leverage in the trade war. The yuan has weakened, which offsets the tariffs by making Chinese exports cheaper. This is the inevitable result of Mr. Trump’s de facto strong-dollar policy, driven by larger budget deficits that have increased foreign demand for U.S. dollars as well as tariffs on China that have reduced U.S. demand for the yuan. Before the latest round of the tariff war, China was helping bring about Mr. Trump’s desired weak dollar by intervening in currency markets to keep the yuan strong. Yet when Beijing gave markets more latitude, the administration branded China a currency manipulator.

In January 2018 China had average tariffs of 8% on imports from the U.S. and the rest of the world. In response to U.S. actions it raised its average tariffs on the U.S. to 20.7% by this June while cutting its tariffs on the rest of the world to 6.7%, according to Chad Bown at the Peterson Institute for International Economics. China has cut its imports from the U.S. but increased its imports from elsewhere. China’s exports to the rest of the world are also growing.

No wonder China isn’t in a hurry to make the major concessions Mr. Trump has demanded.