Okay, I couldn’t look at this table when I responded last night (I thought you were referring to the zip files, not the PDFs at the bottom). Got a chance to look at them on my computer today!

Would you call the point where I_x = 1/2 I_0 the life expectancy at birth? In the life tables you link to (direct link to the 2020 table) there’s an “expectation of life at age x” column which differs! My understanding is that in official metrics of “life expectancy” they usually mean the “life expectancy at birth”, which is calculated in the “expectation of life at age x” column in this data set, do actuaries use a different definition?

In this table “life expectancy at birth” is estimated at 74.2 for men in the USA in 2020. This is calculated in this table by computing T_0 / I_0, which is the arithmetic mean for the ages of death in this period. The estimate for the median age of death in this table is between the ages of 79 and 80. There’s about a 5 year difference between these two numbers, and furthermore only about 40% of the population of men has died by the ages of 74-75 in this table, which is quite different from 50% if we assume “life expectancy” is this arithmetic mean. These are pretty big differences, and I really wish people / articles would be more clear about how the number they’re quoting was actually calculated and what it means! The estimated median age of death from the point I_x = 1/2 I_0 is a useful measure too, but I have no idea what a random person or article intends when they say “life expectancy” :|. I’ve grown to deeply distrust any aggregate measure that people discuss informally or in news articles… It’s often very unclear how that number was derived, what that number actually means in a mathematical sense, and if it even means anything at all.