More on life expectancy:

Reader Mary Campbell, an actuarial assistant in New York writes, based on Social Security Administration tables:

There are two types of mortality tables available — cohort and calendar year. Using the 1900 cohort tables, I find the following probabilities (and life expectancies) (my table does not include mortality before age 5, as early childhood mortality is difficult to get accurate reports on — this is true even today, as many babies are reported as stillborn in other countries who would be counted as born alive here, as we’ve got neonatal intensive care units to try to help these children survive…):

We usually report life expectancy as additional years to live, but to make it simpler, I will report on total lifespan.

For a 10-year-old girl born in 1900:
The lifespan expectancy is 71.5 years
Median lifespan is 77 years.
She has a 25% probability of reaching age 87.

For a 10-year-old boy born in 1900:
The lifespan expectancy is 65.5 years
Median lifespan is 69 years.
He has a 25% probability of reaching age 80.

—

For a 10-year-old girl born in 1950:
The lifespan expectancy is 81.3 years
Median lifespan is 85 years.
She has a 25% probability of reaching age 92.

For a 10-year-old boy born in 1950:
The lifespan expectancy is 75.3 years
Median lifespan is 79 years.
He has a 25% probability of reaching age 87.

—-
For a 10-year-old girl born in 2000:
The lifespan expectancy is 85.3 years
Median lifespan is 88 years.
She has a 25% probability of reaching age 95.

For a 10-year-old boy born in 2000:
The lifespan expectancy is 80.4 years
Median lifespan is 84 years.
He has a 25% probability of reaching age 91.

Now, there are some things being captured here and some things not. Improvements in women not dying from childbirth, improved nutrition, better medicine, and less cigarette smoking may all be involved. The Society of Actuaries does general mortality studies often, to see which factors have had the largest effect — the 1900 cohort would have been impacted by WWI and the Spanish flu outbreak and infectious diseases in general. We pretty much have the complete mortality table for the 1900 cohort now (excepting a few stragglers). The 1950 and 2000 cohort tables are obviously made on model projections for ages past 53 for the 1950 cohort, and for almost all of the 2000 cohort. Time will tell if obesity, diabetes, cardiovascular disease, cancer, and what have you will have a large mortality effect. The main difference is that unlike infectious disease, these conditions do not kill the young as often. Then there is the issue of improved medicines for counteracting horrible lifestyles.

Notice the gender gap is closing for mortality, and some of it may be due to “stupid stuff” guys do in early adulthood, as well as the “protection” — whether hormonal or otherwise — pre-menopausal women get. If you look at age 65 men and women, the life expectancy gap narrows from about 5 years seen above to about 3 years.

I’ve also got those “calendar year” mortality tables you were wondering about, and those are what give the horrible life expectancies. These are harder to interpret, because they just capture the mortality for each age for the year 1900. That mortality structure does not persist past that year (okay, maybe for a few more years). So if I plug in a 10-year-old girl to the 1900 calendar year table, I get a lifespan expectancy of 61.1 years! Ten years less than the cohort table! But that’s assuming it will be 1900 every year.

In the lifetime of that 10-year-old girl (should she survive the Spanish Flu in adulthood), sulfa drugs will be discovered, as will antibiotics. The Pure Food and Drug Act will be passed. With manure-spread roads going away with the advent of cars, the water actually becomes cleaner — less cholera or dysentery, which killed quite a few of the young and elderly. Vaccination becomes widespread. Public sanitation improves.

So the life expectancies reported are much more pessimistic than actuality, even if you skip over the huge childhood mortality period, which greatly drops around age 10. . . .

I got the tables to do the above calculations from the Office of the Chief Actuary of the Social Security Administration (he’s got a website, with all sorts of studies and projections). The Society of Actuaries also has tables (soa.org) as does the American Academy of Actuaries (actuary.org).