http://www.sfu.ca/~allen/LockdownReport.pdf

The question is: how many months would be sacrificed on average? Professor Caplan argues that X = 10 months is a conservative estimate. That is, on average, two months [of life] would be sacrificed to have avoided lockdown. For the sake of argument, suppose this is the true number for the average Canadian.

As of March 2021 the pandemic has lasted one year. That means that the average Canadian has lost two months of normal life. The population of Canada is about 37.7 million people, which means that 6.3 million years of life have been lost due to lockdown.

The average age of reported Covid-19 deaths in Canada is about 80.47 In Canada an average 80 year old has a life expectancy of 9.79 years. This means that the 6.3 million years of lost life is equivalent to the deaths of 643,513 80 year olds. As of March 22, 2021 Canada has had a total of 22,716 deaths due to Covid-19. That amounts to 222,389 lost years of life.

The question is, however, how many lost years of life would have resulted from Covid-19 deaths if there had been no lockdown? Consider two extremes:

a. Assume that the number of Covid-19 deaths would have been 10% higher had there been no lockdown. Then Canada would have experienced an additional 2,271 deaths, which means there would have been additional 22,333 years of lost life due to Covid-19 deaths. The benefit of lockdown, therefore, was the avoidance of this extra 22,333 years of lost life. However, the cost of lockdown, as noted, was 6,300,000 years of lost life. The cost/benefit ratio of lockdown is 282 = 6, 300, 000/22, 333.