Economists know what they don’t know. US President Trump is expected to announce the largest peacetime tax increase in US history. The erratic nature of trade policy, uncertainty about whether legal procedures will be followed, limited clarity about end-objectives, the possibility that Trump will again retreat from some taxes, and the unpredictability of patronage-style deals to gain exemptions create uncertainty about the direct effect of the taxes. The second-round effects depend on unpredictable reactions by US companies, a far more complex global trade system than existed 20 years ago, and US consumers whose reaction to inflation has shifted.