Demographers commonly use life expectancy rates as a measure of societal well-being. The life expectancy rate is the number of years someone is expected to live at the time they are born based on actuarial science. Long life is a universal indicator of prosperity across cultures and time. It is an important measure to demographers because achieving it requires a complex mix of variables, like a sustained nutritious food supply, a sanitary and safe environment, relatively little disease, absence of war, and a stable society.
So what can we say about this measure of prosperity throughout human history? Here are estimates of two social scientists and economists typical of those who study these issues:
For most of its existence, Homo sapiens lived in far-flung hunter-and-gathering communities, each of which was quite small and barely able to reproduce itself. Life expectancy at birth was hardly twenty-five years on average, and those persons who survived childhood often died violently, in combat with other hunters, at relatively young ages. (Robert William Fogel, The Fourth Great Awakening and the Future of Egalitarianism, 48)
For much of human history, average life expectancy used to be 20-30 years. By 1900, it had climbed to about 31 years … By 2003 it was 66.8 years. (Indur Goklany, The Improving State of the World, 31)
To put the last statement by Goklany in perspective lets graph the estimated life expectancy on a chart:
If we show only the last two centuries we get a clearer picture of what has happened:
Using life expectancy as a measure of prosperity, the world is far more prosperous than it has ever been and the gap is narrowing between the top and bottom rungs of the global community. More amazing, most of this change occurred over a time when the total world population grew sixfold, from less than 1 billion in 1800 to about 6.6 billion today!
This is not to say that every nation, or every region within a nation, or every subgroup within in a nation, has prospered equally well. Note the tragic impact of the AIDS epidemic and social chaos has had on sub-Saharan Africa by looking at this map of life expectancy from wikipedia:
The trajectory of change is an unprecedented rise in prosperity. It is uneven growth but every corner of the planet has improved and the gap between top and bottom nations is closing.
Next we look at infant mortality rates.