Who’s Driving a Recent Decline in Life Expectancy?

From 1950 to 2019, life expectancy steadily increased in the U.S., as well as in other countries in the G-7 (Canada, France, Germany, Italy, Japan and the U.K.).“Life expectancy” refers to life expectancy at birth throughout the article. However, life expectancy then declined in many of these countries from 2019 to 2021. The declines from 2019 to 2020 and again from 2020 to 2021 represented the biggest two-year drop in life expectancy in the U.S. since the early 1920s, and it brought U.S. life expectancy to its lowest level since 1996.See the CDC National Center for Health Statistics’ August 2022 press release, “Life Expectancy in the U.S. Dropped for the Second Year in a Row in 2021.” During this period (2019-2021), global life expectancy declined for the first time since the United Nations began collecting such data in its World Population Prospects report.See Patrick Heuveline’s March 2022 article, “Global and National Declines in Life Expectancy: An End-of-2021 Assessment,” in the journal Population and Development Review.

Our goal in this article is to examine mortality data, break down changes in mortality by specific age groups and show how those changes accounted for the decline in average life expectancy.

Calculating Life Expectancy

Life expectancy at birth is the number of years on average that a newborn could expect to live. In general, life expectancy is the additional number of years that a person at a given age could expect to live on average. To calculate life expectancy, we need to know age-specific death rates; i.e., we need to know the probability that a person of age j will die before reaching age j+1. This can be measured in the data by the proportion of age-j individuals who die before they get to age j+1. On the flip side, the age-specific survival rate is the probability that a person of age j will survive one more year, to age j+1.

To use a concrete example, suppose that we want to calculate the life expectancy of a person who is 30 years old at the end of 2022. That is, we want to determine how many additional years this person will live on average. Simple logic dictates that:

• Life expectancy at age 30 = probability that the 30-year-old person survives to age 31 * (1 + life expectancy at age 31).

Similarly, we know that:

• Life expectancy at age 31 = probability that the 31-year-old person survives to age 32 * (1 + life expectancy at age 32).

We could keep adding years ad infinitum. However, we can truncate the process at an age sufficiently high. For instance, we can safely assume that life expectancy at age 125 is zero. (The oldest person on record lived to age 122.) Knowing that the life expectancy at age 125 is zero, we can use an equation similar to the one above to compute life expectancy at age 124. Working backward, we can compute life expectancy at every age, including life expectancy at birth.

Life Expectancy Can Change over a Person’s Lifetime

Two features of this calculation are worth noting. First, measuring life expectancy in 2022 involves using 2022 survival rates or death rates. This means a person’s life expectancy can change during their lifetime if age-specific death rates change. Second, the age composition of the population has no bearing on the calculations. That is, regardless of whether the 2022 population is dominated by older age groups or younger age groups, the life expectancy calculations will yield the same numbers.

For example, according to the United Nations’ World Population Prospects data, life expectancy in the U.S. was 67.5 years in 1950. This number is calculated using the 1950 death rates for ages 0, 1, 2, 3, and so on. Note that, in the World Population Prospects data, ages above 100 are classified as ages 100+. This truncation does not much affect average life expectancy; very few people are more than 100 years old.

The COVID-19 Effect

If life expectancy declined after 2019, then it must be the case that age-specific death rates increased for some age groups. The following table shows age-specific death rates in the U.S. for age groupings of 20 years from 2015 to 2021. The magnitude of the increase from 2019 to 2021 was largest for the 60-79 age group, at 3.63 deaths per 1,000. The second-largest increase in magnitude was for the 80-99 age group. One reason that the largest increases in death rates were clustered in older age groups was likely the rise in deaths due to the COVID-19 pandemic, which were concentrated among people ages 65 and above, according to Centers for Disease Control and Prevention (CDC) data.See COVID-19 mortality data from the CDC National Center for Health Statistics, reported as of June 2023 in “Excess Deaths Associated with COVID-19.”

Who Contributed Most to the Decline?

To determine which age group contributed the most to the life expectancy decline in the U.S. from 2019 to 2021, we ran a counterfactual experiment. We held the death rate for each age from 0 to 19 fixed at 2019 levels. We left the death rates for the other age groups as they are in the table data. We then calculated the life expectancy at birth in 2020 and 2021 using these counterfactual death rates.

The dashed orange line in the figure below shows the results from this experiment. The dashed orange line is not substantially different from the figure’s solid black line, which illustrates the actual decline in life expectancy. Thus, we can conclude that changes in the death rate for Americans ages 0-19 did not much contribute to the drop in life expectancy.

We then repeated this experiment for every other age group, one at a time. The figure above shows these results as well. In the counterfactual experiment, when death rates are fixed at 2019 levels, life expectancy for the 60-79 age group is substantially different from the actual life expectancy value. In fact, this counterfactual result, denoted in blue, is the most different from actual life expectancy relative to other counterfactual outcomes. Thus, this age group was the primary driver of the decline in U.S. life expectancy.

Life Expectancy among Other Nations

The next figure examines the same set of counterfactual experiments for Germany, another member of the G-7. In Germany, life expectancy declined in both 2020 and 2021, with death rates in the 80-99 age group driving the decline.

These counterfactual results vary across the rest of the countries in the G-7. However, life expectancy declines from 2019 to 2021 were driven by death rates in the 60-79 age group in France, Italy and the U.K.Life expectancy increased from 2019 to 2021 in Canada and Japan.

In sum, life expectancy declines in the U.S. from 2019 to 2021 were driven by the 60-79 age group. Life expectancy changes for other countries in the G-7 varied, but declines also were driven by elderly age groups.

Notes

1. “Life expectancy” refers to life expectancy at birth throughout the article.
2. See the CDC National Center for Health Statistics’ August 2022 press release, “Life Expectancy in the U.S. Dropped for the Second Year in a Row in 2021.”
3. See Patrick Heuveline’s March 2022 article, “Global and National Declines in Life Expectancy: An End-of-2021 Assessment,” in the journal Population and Development Review.
4. See COVID-19 mortality data from the CDC National Center for Health Statistics, reported as of June 2023 in “Excess Deaths Associated with COVID-19.”
5. Life expectancy increased from 2019 to 2021 in Canada and Japan.