On the face of it, China and the United States both look as though they would be relatively insulated if trade tensions continue to escalate.

China's exports to the U.S. account for only 4 percent of its GDP, and its imports from the U.S. amount to just 1 percent of GDP. In the U.S., with its large, domestically driven economy, the equivalent figures are 1 percent and 3 percent. But putting aside these headline numbers, a retreat from globalization by the world's two largest economies would nonetheless entail significant costs.

True, China has been rebalancing away from exports: Domestic consumption contributed to more than 60 percent of its GDP growth in 10 of the 15 quarters since 2015, and up to 80 percent in the first half of 2018.