Data show that compulsory lockdowns have had a high cost, with a questionable impact on transmission.
In 1932, Justice Louis Brandeis of the Supreme Court famously referred to the states as "democracy laboratories." Different states can test different policies and can learn from each other. In 2020, that proved valid. Governors in various states react to the COVID-19 pandemic at different times and in different ways. Sweeping shutdowns were ordered by some states, such as California. A more targeted approach was taken by others, such as Florida. Others, such as South Dakota, transmitted data but had no lockdowns at all.
As a consequence, to test the question no one wants to ask, we can now compare findings in various states: Did the lockdowns make a difference?
If the course of this pandemic was really altered by lockdowns, then the coronavirus case counts should have fallen clearly whenever and wherever lockdowns took place. The effect, albeit with a time lag, should have been apparent. It takes time to formally count new coronavirus infections, so we'd expect the numbers to fall as soon as the waiting time is over.
For how long? New infections should drop on day one and be noticed about ten or eleven days from the beginning of the lockdown. The number of patients with the first signs of infection should decrease by day six (the average time for symptoms to show is six days). By day nine or ten, far fewer people will be going to hospitals with deteriorating symptoms. If COVID-19 tests were conducted immediately, we would expect the positives to drop dramatically on day 10 or 11 (assuming rapid test turnarounds).
To judge from the evidence, the answer is clear: Mandated lockdowns had little effect on the spread of the coronavirus. The charts below show the daily case curves for the United States as a whole and for thirteen U.S. states. As in almost every country, we consistently see a steep climb as the virus spreads, followed by a transition (marked by the gray circles) to a flatter curve. At some point, the curves always slope downward, though this wasn’t obvious for all states until the summer.