Price of Delay in COVID-19 Lockdowns: Delays Spike Total Cases, Natural Experiments Reveal

Governors of US States ordered mandatory lockdowns on different dates across the US. The authors identify natural experiments consisting of cohorts of similar neighboring states with different lockdown dates. The authors analyze COVID-19 penetration per million population within these cohorts, adjusting for the start date of the disease in each state. Here are the major results. All states show a substantial decline in the growth of COVID-19, with total penetration tending to level off after rising steeply initially. This decline is probably due to better hygiene, social distancing, and mandatory lockdowns. However, big differences exist within cohorts of similar neighboring states that differ only in date of mandatory lockdowns. • Those states that locked down late suffered a 15% to 25% higher penetration of the disease, per week late in date of shutdown, as of May 1st 2020. Moreover that difference is widening. • Those states that did not lock down suffered a 45% to 128% increase in total cases relative to those that did lockdown, as of May 1st 2020. Moreover, this difference is widening. • The strength of these results resides not only in the care of constructing the natural experiments but also in the fact that results from all six of them are consistently in the same direction, supporting the alternate hypothesis. In addition, the authors identify one natural experiment between one state that had a huge social mixer (Mardi Gras in Louisiana, attracting millions of tourists over two weeks) and another similar neighboring state without such an event. The state with the social mixer shows a big increase of almost 4,000 cases per million of population, amounting to a huge 163% increase in the penetration of the disease. These findings suggest that policy regarding response to pandemics should be informed by Federal agencies and scientists with the resources to forecast pandemics, rather than be left solely to state governors or local officials who lack such resources. Governors are now considering reopening their states. Learning from the cost of delay in locking down the state would help them to make an informed decision about the true value of lockdowns.