Blame foreigners first. This strategy is always the companion of aggrieved nationalism. It can be seen in Donald Trump’s ban on immigrants from seven countries. It will be seen in his protectionism. A kernel of truth — terrorism and the direct impact of imports on jobs — bolsters a lie: my actions are enough to keep you safe and restore the prosperity you once knew.

At the heart of the US debate on trade policy is the story of jobs in manufacturing. The single most important fact is the steady decline in the share of jobs in manufacturing from about 30 per cent of total employment in the early 1950s to just over 8 per cent at the end of 2016.

The main explanation for the long-term decline in the share of manufacturing employment in the US (and other high-income economies) has been the rise in employment elsewhere. In 1950, employment in manufacturing was 13m, while that in the rest of the economy was 30m. By the end of 2016, it was 12m and 133m, respectively. Thus, all the increase in employment between 1950 and the end of 2016 occurred outside manufacturing. Yet output of US manufacturing was not stagnant. Between 1950 and 2016, output rose 640 per cent, while employment fell 7 per cent. Even between 1990 and 2016 output rose 63 per cent, while employment fell 31 per cent. (See charts.)