At the strike of midnight on September 1, the White House fired another salvo of shots in its heating trade war with China, raising tariffs on $112 billion worth of Chinese imports. The costs of the rounds of tit-for-tat trade measures are mounting. For the US, average tariffs as a share of 2018 import values are now 5.5 per cent, having risen from 1.7 per cent in December 2017. And more is coming: already pre-announced tariffs hikes will see these figures rise to 6 per cent by the end of 2019. Explicit and implicit restrictions on trade in specific goods…