Once the immediate danger of a natural disaster subsides, and the loss of life, property damage, cost of rebuilding, and degree of insurance coverage can be assessed, attention generally turns to the economic effect. How will Hurricane Harvey affect the nation’s gross domestic product?

You will no doubt hear assertions that the rebuilding effort will provide a boost to contractors, manufacturers and GDP in general. But before these claims turn into predictable nonsense about all the good that comes from natural disasters, I thought it might be useful to provide some context for these sorts of events.

Over the years, I’ve observed a tendency among economists and traders to view such events through a demand-side prism. They see lost income translating into reduced spending on goods and services, which might even warrant some largesse from the central bank.

Of course, that is precisely the wrong medicine. Supply shocks reduce output and raise prices. The Federal Reserve’s interest-rate medicine affects demand. Lower interest rates will increase the demand for gasoline, among other goods and services, but they have no effect on supply. An easing of monetary policy under such circumstances would increase demand for already curtailed supply, raising prices even more.