New data show that quarantining the healthy is even worse than critics thought. The spread of Covid-19 around the world prompted extraordinary, although often untested, steps by individuals and institutions to limit infections. Schools, restaurants, entertainment venues, and many other places of business were required to close under the compelling theory that infectious diseases spread more quickly when people congregate. As the end of the pandemic's third year approaches, China continues to require millions of people to stay at home.

With more than two years of data now available, it is apparent that even the critics of lockdowns – isolating large groups of people who are more than 99 percent likely to be uninfected – underestimated the costs and overestimated the benefits.

The purported benefit is to slow the spread of the disease until vaccines and treatments become available to reduce mortality from the disease. In many cases, lockdowns accelerated the spread rather than reducing it because the demand and supply of prevention are greater when people work together in large groups than when they are isolated in small ones. Of all places, China should be most aware of how unproductive people can be when the state requires that they produce in small groups. Chairman Mao's so-called Great Leap Forward required villagers to produce steel in their backyards, with the result of much waste and little useable steel because production is only feasible in much larger plants. We saw in the U.S. that large groups can be pretty effective at slowing the spread, with teachers, students, doctors, nurses, and others getting (on an hourly basis) more Covid infections at home than at work or school.

Travel restrictions have sometimes worked. Hawaii delayed Covid deaths until vaccines became available, thereby reducing long-run total deaths by about 2,000. But Hawaii's economy suffered. I estimate that saving the 2,000 lives cost $8–11 million each, which is high but not so different from the kinds of trade-offs that many private citizens make in their own lives.

China should not expect the same results because, without Hawaii's geographic advantages, isolating its cities costs much more. Moreover, with vaccines and treatments already available, non-pharmaceutical interventions will largely delay Covid deaths rather than reduce or prevent them. Again, the U.S. provides lessons: Mainland blue states with stringent Covid policies shrank their economies and imposed long-lasting costs on children without any noticeable health benefit.

Although conceived and promoted by public-health officials, pandemic policies harmed health, too. Deaths from drugs and alcohol were already high before the pandemic, yet health officials failed to monitor whether their policies during the pandemic were exacerbating them. The result in the U.S. was an increase in alcohol and drug mortality of 20 to 30 percent above trend.

In a forthcoming paper, Rob Arnott and I look at all causes of death and compare them with mortality rates before the pandemic. From April 2020 through the end of 2021, Americans died from non-Covid causes at an average annual rate of 97,000 in excess of previous trends. Preliminary analysis suggests that excess mortality continues into calendar year 2022 at an equally high rate. As magnitudes for comparison, we note that, converted to dollars at a $10 million average value of a statistical life, the non-Covid excess deaths in the U.S. through the end of 2021 cost more than a trillion dollars. In addition to these mortality costs are many other health and economic costs totaling trillions of dollars in the U.S. alone.

With so many costs and so few benefits, it is no wonder that Chinese citizens are risking life and liberty to protest their country's ongoing pandemic policies.

Casey B. Mulligan is a professor of economics at the University of Chicago's Kenneth C. Griffin Department of Economics, and served as the chief economist of the White House Council of Economic Advisers in 2018–19. He is also the author of You're Hired! Untold Successes and Failures of a Populist President, which details conflicts between President Trump and special interests.