lockdown chart

Updated 21/4/20
According to a study discussed today in the Wall Street Journal (behind a paywall), the nationwide lockdown was never necessary. The vast majority of states should have followed Sweden's example:
We ran a simple one-variable correlation of deaths per million and days to shutdown, which ranged from minus-10 days (some states shut down before any sign of Covid-19) to 35 days for South Dakota, one of seven states with limited or no shutdown. The correlation coefficient was 5.5% — so low that the engineers I used to employ would have summarized it as "no correlation" and moved on to find the real cause of the problem. . . .
Sweden is fighting coronavirus with common-sense guidelines that are much less economically destructive than the lockdowns in most U.S. states. Since people over 65 account for about 80% of Covid-19 deaths, Sweden asked only seniors to shelter in place rather than shutting down the rest of the country; and since Sweden had no pediatric deaths, it didn't shut down elementary and middle schools. Sweden's containment measures are less onerous than America's, so it can keep them in place longer to prevent Covid-19 from recurring. Sweden did not shut down stores, restaurants and most businesses, but did shut down the Volvo automotive plant, which has since reopened, while the Tesla plant in Fremont, Calif., was shuttered by police and remains closed.
How did the Swedes do? They suffered 80 deaths per million 21 days after crossing the 1 per million threshold level. With 10 million people, Sweden's death rate ‒ without a shutdown and massive unemployment ‒ is lower than that of the seven hardest-hit U.S. states — Massachusetts, Rhode Island, Louisiana, Connecticut, Michigan, New Jersey and New York — all of which, except Louisiana, shut down in three days or less. Despite stories about high death rates, Sweden's is in the middle of the pack in Europe, comparable to France; better than Italy, Spain and the U.K.; and worse than Finland, Denmark and Norway. Older people in care homes accounted for half of Sweden's deaths.
History will record the one-size-fits-all economy-destroying COVID-19 lockdown of 2020 as one of the most colossal public policy blunders in the history of the world.