The old certainties are falling fast. Mars bars and Snickers are being recalled in Europe because of contamination with plastic bits. The Great Trunk Road walked by Kipling’s Kim, friend of all mankind has been blocked by an Indian caste who want to be treated as untouchables. Even the lessons of the 1930s about how to exit a depression are being revised.

The US will ask G20 countries meeting in Shanghai this weekend to use fiscal rather than monetary policy to increase global demand, a senior Treasury official told Reuters. American officials will urge G20 members to meet their commitment to refrain from manipulating exchange rates for competitive advantage. But to get around the obstacles to beggar-my-neighbor exchange rate fiddles in democratic countries you only need political mavericks heading for power. In the US, The Donald Trump. In Britain, The Boris Johnson.

Yesterday after Boris came out against Britain remaining in the EU, the pound sterling fell to a 7-year low. The pound fell another 0.4% against the dollar yesterday’s morning.

The macro-economic advantage from Boris Johnson’s call for British exit from the European Union, AKA Brexit, is sterling’s decline. Cheaper pounds mean British firms can sell more goods and services outside the country. Sterling’s decline also makes it harder for Britain to import stuff. Cheaper sterling will also push up the UK rate of inflation and boost GNP growth and employment.

Meanwhile good-guy governments listening to the US Treasury face problems meeting growth and inflation targets if they do not act to depreciate their currencies.

The British currency is declining because of uncertainty about Brexit and possible harm to the UK economy if Britain leaves the EU, but the impact on British stocks and bonds is mixed. The weaker currency fits the UK government goal of boosting inflation, employment, and growth. So far its 2% inflation target is way out of reach, while growth is feeble in Britain as elsewhere. Without having to break the rules by depreciating sterling, Britain is gaining a macro-economic advantage from Boris.

The Governor of the Bank of England, Mark Carney, now hints that British interest rates should be cut this year rather than increased. The base rate now is 0.5% but now it may be lowered because the economy needs more stimulus particularly because the global economy is falling. With Boris, Gov Carney doesn’t need to cut rates to under zero as Japan, Denmark, Norway, and EU have done.

The other wild blond politician, Donald Trump, can impact the dollar similarly if he gets closer to winning the Republican nomination. Imagine what a Trump triumph would achieve in the US! The dollar would lose height for fear of the unfunded tax cuts and government measures he advocates.

As soon as he captures the nomination, a pre-election panic among companies exporting to the US would boost our imports and further undermine the Greenback. Mexico would ship 18 months worth of cars and chemicals to its northern neighbor. China would end the global shipping glut by sending 5 years worth of gizmos, appliances, cellphones, and garments in advance.