Despite the rhetoric around decentralisation, digital currencies and the prospect of a more diversified monetary future, the dollar remains the most important benchmark in the global economy. This is so in the conventional foreign exchange market, where the dollar is still the pivot point for trade, reserves and risk. It is also true in crypto, where speculators may talk about the advent of financial alternatives, but still track value, liquidity, and sentiment in dollar terms. The upshot is that the dollar remains the lead actor in both forex and crypto, a fact that market participants keep rediscovering.

That is important because it alters the way we view both markets. In forex, for example,…