Buying time for the post-COVID reckoning

The U.S. stock market has had an extraordinary week, with the broad S&P 500 index rising nearly 12 percent since Monday. Investors seem to believe that the actions of the Federal Reserve in particular — which announced a new $2.3 trillion effort to support local governments and small- to mid-sized businesses — will substantially limit the economic damage caused by shelter-in-place orders and other physical-distancing efforts to combat the virus, and set the economy up for a quick rebound once the crisis is over.

Are they right? It's impossible to...