Joel E. Cohen is a mathematical biologist and Professor of Populations at Rockefeller and Columbia Universities. His research deals with the demography, ecology, epidemiology and social organization of human and[…]
In wealthy nations across the world, population growth rates have rapidly declined from their peak in 1965. The reasons behind this are varied and rife with complications, as scientists still don’t know why people choose to have children.
Question: Why are population rates declining in wealthy nations?
Joel Cohen: You have asked the $64 million question. And demographers believe they have answers, but they are partial, Monday morning quarterbacking after the fact. So the truth is that nobody predicted ahead of time that the world's population growth rate would peak at 2.1% per year in 1965 and then fall by half by 2000. Nobody predicted that. On the other hand, fertility began to fall around 1750 in France, before the French revolution, before the invention of the condom, before there was literacy, before there was women's rights, why? Because the nobility didn't have enough lands to tax to feed all of their sons, forget the daughters, the sons got the land. So we know from the records that the nobles of France started reducing the number of children they have from natural, compared to natural levels of fertility. They spaced them and they stopped having them earlier because they couldn't, there weren't enough people to tax. The peasants saw what the nobles were doing and they didn't have enough land to divide up among their children, so they started reducing the number of their children. So if they didn't have condoms and they didn't have the pill, which hadn't been invented, and they didn't have diaphragms, they didn't have IUD's, what did they do? You tell me. What did they do? Withdrawal, coitus interruptus. Okay? It's perfectly effective if you really are serious about it, okay, I don't recommend it as a practice today, it's too risky, but statistically, it worked.
So fertility in France declined, began to decline around 1750 and has continued. When did fertility begin to decline in the United States? Do you know? Civil war. After the civil war, began to decline and has continued to decline. It dropped during the Depression in the '30's, spiked at the baby boom after the war, but has dropped back down. The only reason it's as high as it is now is due to immigrants, who have higher levels of fertility, but even within immigrant population, within a generation, it falls back to the level of the native born population. Okay?
This shows that any simple answer I could give to your question would be wrong. Because in some countries, education makes a huge difference, and in some countries, economics makes a huge difference, and in some countries, you know, technology makes a huge difference, having the pill and contraceptive devices available. So it's multi-factorial and we don't have a good theory to explain the past and we have even less understanding of what will happen in the future. Let's take countries that are in decline now, Russia is using a million people a year roughly. Japan is in decline, Russia is in decline, Germany is in decline. Will those countries ever have a level of fertility that picks up enough to keep them from going out of business? If you can answer that question? You get the gold star, because we don't know. And demographers make different scenarios about the future, but the honest fact is, we don't know what the future will bring in that dimension because we don't have a basic understanding of why people choose to have children.
Joel Cohen: You have asked the $64 million question. And demographers believe they have answers, but they are partial, Monday morning quarterbacking after the fact. So the truth is that nobody predicted ahead of time that the world's population growth rate would peak at 2.1% per year in 1965 and then fall by half by 2000. Nobody predicted that. On the other hand, fertility began to fall around 1750 in France, before the French revolution, before the invention of the condom, before there was literacy, before there was women's rights, why? Because the nobility didn't have enough lands to tax to feed all of their sons, forget the daughters, the sons got the land. So we know from the records that the nobles of France started reducing the number of children they have from natural, compared to natural levels of fertility. They spaced them and they stopped having them earlier because they couldn't, there weren't enough people to tax. The peasants saw what the nobles were doing and they didn't have enough land to divide up among their children, so they started reducing the number of their children. So if they didn't have condoms and they didn't have the pill, which hadn't been invented, and they didn't have diaphragms, they didn't have IUD's, what did they do? You tell me. What did they do? Withdrawal, coitus interruptus. Okay? It's perfectly effective if you really are serious about it, okay, I don't recommend it as a practice today, it's too risky, but statistically, it worked.
So fertility in France declined, began to decline around 1750 and has continued. When did fertility begin to decline in the United States? Do you know? Civil war. After the civil war, began to decline and has continued to decline. It dropped during the Depression in the '30's, spiked at the baby boom after the war, but has dropped back down. The only reason it's as high as it is now is due to immigrants, who have higher levels of fertility, but even within immigrant population, within a generation, it falls back to the level of the native born population. Okay?
This shows that any simple answer I could give to your question would be wrong. Because in some countries, education makes a huge difference, and in some countries, economics makes a huge difference, and in some countries, you know, technology makes a huge difference, having the pill and contraceptive devices available. So it's multi-factorial and we don't have a good theory to explain the past and we have even less understanding of what will happen in the future. Let's take countries that are in decline now, Russia is using a million people a year roughly. Japan is in decline, Russia is in decline, Germany is in decline. Will those countries ever have a level of fertility that picks up enough to keep them from going out of business? If you can answer that question? You get the gold star, because we don't know. And demographers make different scenarios about the future, but the honest fact is, we don't know what the future will bring in that dimension because we don't have a basic understanding of why people choose to have children.
