About that one-year decline in life expectancy

February 25, 2021

Topic

Statistics  /  , ,

The Centers for Disease Control and Prevention released a report that said life expectancy decreased by a full year in 2020. While the calculation is correct, the interpretation and message from that number is more challenging. For STAT, Peter B. Bach provides context to the measurement:

Don’t blame the method. It’s a standard one that over time has been a highly useful way of understanding how our efforts in public health have succeeded or fallen short. Because it is a projection, it can (and should) serve as an early warning of how people in our society will do in the future if we do nothing different from today.

But in this case, the CDC should assume, as do we all, that Covid-19 will cause an increase in mortality for only a brief period relative to the span of a normal lifetime. If you assume the Covid-19 risk of 2020 carries forward unabated, you will overstate the life expectancy declines it causes. […]

Bach wonders if the CDC should have released the report at all, if most people were just going to misunderstand it. That seems like the wrong direction though. Life expectancy is a useful metric, and if you know there are a lot of chances for miscommunication, you try your best to explain the numbers with the audience in mind.