THAT’S AMAZING! IF THEY WERE ABLE TO DO THAT, THEN I’M ALL FOR ‘EM! Did COVID-19 Lockdowns Reach Back in Time to Affect Behavior Before They Were Imposed?

Zimmer links to a chart that shows the reproductive number in Massachusetts falling precipitously in March. But that downward trend began more than three weeks before Gov. Charlie Baker issued his business closure and stay-at-home orders. By the time Massachusetts officially locked down on March 24, the number had fallen from 2.2 to 1.2. That decline continued during the lockdown, falling to a low of 0.8 by May 18, when the stay-at-home order expired and Baker began allowing businesses to reopen. It is therefore possible that closing “nonessential” businesses and telling people to stay home except for government-approved purposes reinforced the preexisting trend. But the lockdown had no obvious impact on the slope of the curve.

The reproductive number continued to fall sharply until the end of March, when it dropped below one, which indicates a waning epidemic. The drop then slowed, and the number fluctuated, going up and down a bit but always staying below one. Since the lockdown was lifted, the picture has stayed pretty much the same. The estimate for yesterday was 0.8, which is a bit surprising if you believe the lockdown was crucial in keeping the number low. Although it has been more than a month since Baker started reopening the state’s economy, virus transmission has not been notably affected.

But politicians can’t take credit for things people do voluntarily.