Everywhere in the world women live longer than men – but this was not always the case. The available data from rich countries shows that women didn’t live longer than men in the 19th century. Why do women live so much longer than men today, and why has this advantage increased over time?
The evidence is limited and we only have partial answers. We know that biological, behavioral and environmental factors all contribute to the fact that women live longer than men; but we don’t know exactly how strong the relative contribution of each of these factors is.
Independently of the exact weight, we know that at least part of the reason why women live so much longer than men today, but not in the past, has to do with the fact that some key non-biological factors have changed. What are these changing factors? Some are well known and relatively straightforward, like the fact that men smoke more often. Other are more complicated. For example, new evidence shows that in rich countries the female advantage increased in part because infectious diseases used to affect women disproportionately a century ago, so advances in medicine that reduced the long-term health burden from infectious diseases, especially for survivors, ended up raising women’s longevity disproportionately.
The first chart below shows life expectancy at birth for men and women. As we can see, all countries are above the diagonal parity line – this means in all countries a newborn girl can expect to live longer than a newborn boy.1
Interestingly, this chart shows that while the female advantage exists everywhere, the cross-country differences are large. In Russia women live 10 years longer than men, in Bhutan the difference is less than half a year.
Let’s now look at how the female advantage in longevity has changed over time. The next chart plots male and female life expectancy at birth in the US over the period 1790-2014. Two points stand out.
First, there is an upward trend: Men and women in the US live much, much longer today than a century ago. This is in line with historical increases in life expectancy everywhere in the world.
And second, there is a widening gap: The female advantage in life expectancy used to be very small, but it grew substantially over the last century.
Using the option ‘change country’, at the bottom of the chart, you can check that these two points also apply to the other countries with available data, Sweden, France and the UK.
(NB. In case you are curious, the big dip in life expectancy in the US around 1918 corresponds to the Spanish flu pandemic.)
The female advantage in life expectancy is partly, but not entirely driven by higher chances of surviving childhood
In poor countries where child mortality is high, these sex differences in mortality are obviously an important factor driving differences in life expectancy. But in rich countries, where fewer children die, and where sex differences in infant mortality are very small, the male disadvantage in infant mortality cannot explain much of the observed differences in life expectancy.
Available evidence shows that child mortality rates in today’s rich countries were higher for male than female infants in the 19th century, and the male disadvantage in child mortality grew through the first half of the 20th century, as health outcomes improved. Similarly, maternal mortality in these countries used to be very high, and it decreased dramatically over the 20th century.
However, as the next chart shows, in France, Sweden, the US and the UK, the life expectancy of women conditional on reaching age 45, was also higher than that of men, and the difference grew through the first half of the 20th century reaching a peak between 1970 and 1980.
Changes in child and maternal mortality do have an impact on life expectancy differences between men and women, but they cannot fully explain the rise in the longevity gap that we’ve observed in rich countries over the last century.
(NB. For the same countries plotted in the chart below, you can explore long-run differences in life expectancy at ages 0, 15 and 45 in this interactive chart)
The evidence shows that differences in chromosomes and hormones between men and women affect longevity. For example, males tend to have more fat surrounding the organs (they have more ‘visceral fat’) whereas women tend to have more fat sitting directly under the skin (‘subcutaneous fat’). This difference is determined both by estrogen and the presence of the second X chromosome in females; and it matters for longevity because fat surrounding the organs predicts cardiovascular disease.3
But biological differences can only be part of the story – otherwise we’d not see such large differences across countries and over time. What else could be going on?
We do not have a definitive answer, but we do have some clues. For example, we know that changes in smoking habits among men have affected mortality patterns.4 And we know that historical medical advances have affected health outcomes for men and women differently. A new study by Adriana Lleras-Muney and Claudia Goldin, looking at long-run data on infectious diseases, gives us insights into this mechanism.5
Lleras-Muney and Goldin show that in the US, infectious diseases disproportionately affected females between the ages of 5 and 25 in the 19th century, so as the burden of infectious disease fell for both men and women, it disproportionately helped women.6
We know that the longer lifespan of females is common in other animals, but it is not universal.7 We also know that biological, behavioral and environmental factors all contribute to the fact that women live longer than men; but we don’t know exactly how strong the relative contribution of each of these factors is.
As the next chart shows, in most countries for all the primary causes of death the mortality rates are higher for men. More detailed data shows that this is true at all ages; yet paradoxically, while women have lower mortality rates throughout their life, they also often have higher rates of physical illness, more disability days, more doctor visits, and hospital stays than men do.8 It seems women do not live longer than men only because they age more slowly, but also because they are more robust when they get sick at any age. This is an interesting point that still needs more research.
An interesting point raised in the study by Adriana Lleras-Muney and Claudia Goldin, is that the disproportionate longevity gain that women enjoyed from reductions in infectious diseases in the 20th century across rich countries, was not about direct benefits from reduced mortality. The direct reduction in deaths due to infectious diseases was important, but it was not the main factor explaining the growth in the life expectancy gap between men and women. In terms of the gap, what seems to have made a difference was the long-run indirect effect for survivors: Those who survive infectious diseases often carry a health burden that affects organs and this makes them more vulnerable later on in life. Rheumatic fever, for example, often damages the valves of the heart and leads to rheumatic heart disease later in life.
This relationship between infectious disease in early life and later-life health has been recognized in the medical sciences; but there are few estimates of the impact at the population level. So the sizeable impact on life expectancy found by Lleras-Muney and Goldin actually has practical relevance for policy today – it suggests that in places where mortality from infectious diseases remains high, the return from investing in treating these diseases may be much larger than we think, because of the long-run indirect health benefits for survivors.
As we were writing this article we reviewed many academic articles, some of which are not directly referenced in the text above. We have compiled them in this short literature review document.