THE world's most ambitious free-trade deal in decades is all but dead. Donald Trump has said that on his first day in office America will quit the Trans-Pacific Partnership (TPP), a pact that was nearly a decade in the works. Encompassing 12 Pacific Rim countries, including America, Japan and Canada, the TPP would have covered nearly two-fifths of the global economy. Mr Trump had called it a “horrible deal” on the campaign trail. In declaring his intent this week to withdraw from it, he said it was “a potential disaster for our country”. But proponents say it would have been a big improvement on existing trade deals and very good for America. Which view is right, and what happens now?
Measuring the precise impact of trade deals that have been in place for years is hard enough. Forecasting the impact of future deals is even harder. Nevertheless, many economists would agree with two general statements. On one hand, TPP would have generated more growth for all inside the agreement. A series of independent studies predicted that America would have reaped the biggest gains in dollar terms and that emerging markets, especially Vietnam, would have benefited most relative to their size. On the other hand, while free-trade deals enrich countries in general, downsides can be severe for industries and regions that lose out. Moreover, recent research has showed that these negative effects are often longer lasting than optimists had once believed. The TPP would, in other words, probably have increased America’s growth, but at least some people would have been justified in thinking it horrible.

But looking at the impact on GDP alone is too narrow.