I’ve often read that the disparity comes at the point of basic data collection. For example, some nations don’t count infant and child deaths against the average. If one nation counts a dead infant against the lifetime longevity average and another country does not account for deceased infants at all, the resulting “average lifespans” will be wildly skewed and not reflective of reality.
My genealogy research has caused me to seriously question longevity numbers.
I’m finding a lot of male ancestors in the 1600s living well into their 80s. The highest mortality rate was among children under 10 years old with frontier women having a very high death rate which I attribute to them spending so many years pregnant.
A similar issue affects infant mortality statistics. Many countries do not include infants who die shortly after delivery, especially premature infants, in their “infant mortality.” The United States does.
You need to understand math to suss this out.
If you are talking about AVERAGE then the numbers are skewed by the extremes. For example, if Bill Gates walks into a room, the average wealth of everyone in the room goes up astronomically.
Likewise, if a country has a high infant/child mortality rate, this will skew the numbers way downward since you are averaging in very low numbers with all the median numbers and high numbers.
The same thing is true of those who say that men don’t live as long ON AVERAGE as women in the USA. Two things make that true but don’t tell the real truth.
1. Male babies die at a higher rate than female babies
2. Young males (15-25) die at higher rate than young females (car accidents, accidents in general, military service). This used not to be true when young women died more often in childbirth or from complication from childbirth (sepsis), but the advent of modern medicine and antibiotics changed that.
So that is how they arrive at the women live longer than men on average. If you start averaging after people have reached age 50, men and women have a more equal rate of longevity. This is because all the low age numbers are eliminated from the averages.
It’s just math.