Here's one key thing you should know about Trump's shock to the world economy: it could work

It's less than a week since Donald Trump's sensational announcement that he was unilaterally ending the world's trading system with the imposition of a 10% minimum tariff for trading with the US - and a very much higher rate for those countries unfortunate enough to have the US as a major export partner. Long-term allies such as Japan and South Korea have been hammered with tariffs of around 25%, while export-dependent poorer countries such as Vietnam, which sells about a third of its exports to the US, have been hit with tariffs in excess of 45%. A further round of…