Donald Trump is a rare thing as far as markets are concerned. The usual maxims do not apply — in particular that one should buy the rumour and sell the fact.
This old saw commends spotting a trend early to maximise returns; buying into something before others catch on and its price goes up.
It works when things indicated or hinted at come to pass. But that simply doesn't apply to the man who will be inaugurated on Monday as US president for the second time.
In the run-up to his inauguration, Trump has raised the idea of annexing Canada, invading Greenland and raising tariffs to protect the US economy — all wild and impactful policy ideas.
But all of it means nothing until he takes office next week. Then we will see which ideas come to fruition, and which were negotiation ploys, or just moments of Fox News-induced inspiration.
In the short-term, much can be earned from the market gyrations induced by what Trump says. Much can be lost too. It is clearly no strategy for long-term capital markets participants.
"You can make a lot of money trading what he says," one senior investment banker told GlobalCapital this week. "And you can lose a lot of money trading what he does."
The reverse is also true. But for a president whose thinking seems to switch so often, and whose policy bark is often worse than his bite, seeing what makes it into law is the only feasible option.
Whether that is good or bad for the capital markets is, of course, an entirely different question. But after months of speculation the markets are about to find out what they should buy into and what they can ignore.