How will longer lives affect world population? Certainly anything that keeps people alive longer will increase the number alive at any given point. However, the details of population growth can be rather counterintuitive. Consider that today the countries with the longest life expectancies at birth have populations that are remaining steady or even shrinking. For example, the UN Population Division expects the populations of Japan, Italy, Germany, and Spain to all decrease over the next 50 years, despite the fact that Japan has the highest life expectancy of any large country, and the Western European nations are not far behind. At the other extreme, the countries with the fastest growing populations are those with relatively low life expectancies – countries like India, China, Pakistan, and Nigeria.
Throughout most of human history, birth rates and death rates were both extremely high. In the year 1000 AD, birth rates were around 70 births per 1000 people per year, and death rates were about 69.5 deaths per 1000 people per year. So each year a town of 1000 people would on average increase its population by half a person. That’s a 0.05 percent rate of growth.
As societies advance, nutrition, sanitation, and medicine all serve to lower the death rate. When births outstrip deaths, population soars, as happened through the twentieth century. But in the last few decades the birth rate has also dropped sharply, particularly in the rich developed nations of the world. As countries gain in wealth and education, and especially as women in those countries gain greater rights, resources are increasingly devoted to education and career, rather than raising a family. This demographic trend is spreading from Europe, Japan, and North America to the rest of the world. Worldwide the birth rate is now 21 births per year per 1,000 people. The death rate is around 10 deaths per year per 1,000 people. So overall the world population is growing at roughly 1 percent, slower than at any time in the last few centuries.
