Russia is complaining that Ukraine’s grain exports are not going to poor countries, undermining the intent of the grain corridor agreement. There is the threat to undue or rewrite that agreement. More than 2 million tons of grain have been shipped over the last five weeks and while not all of it may have gone to poor countries, Moscow is intentionally ignoring the fact that the global grain trade is a single, fungible pie.  For example, wheat is amongst the easiest of traded goods to be estimated and replaced according to weight, measure, and amount. The problem with the war was not that Ukraine’s wheat was not getting say Africa, but that its supply was removed from the total global tradable stock. Much as Russia’s...