China’s current-account surplus was once one of the most controversial statistics in economics. The figure, which peaked at almost 10% of gdp in 2007, measures the gap between China’s earning and its spending, driven largely by its trade surplus and the income it receives from its foreign assets. For much of the past two decades, China’s surpluses have left it open to the charge of mercantilism—of stealing jobs by unfairly boosting its exports. Some trading partners now worry about a similar shock if the country’s output of electric vehicles grows too quickly.