The demographic transition model

This is my grandmother. She had eight children! And here am I with my four siblings. And there's only two of you... ah, families are getting smaller and smaller.

Today's news: The world population continues its rapid increase! The biggest growth is in poorer countries... Earth's population is increasing, but it's not increasing at the same speed in all countries. In countries where many are very poor, the population is increasing quickly. But in Europe, for instance, which is relatively wealthy, the population increase is low.

Wealth and population increase seem to be connected. But how? Let's look back at how Europe has changed while becoming rich. We start in 18th century Europe. Most people are poor farmers.

Everyone needs to work if the family is going to survive. That's why it's good to have many children; they are an important workforce. But diseases spread easily and many children die at an early age. So, even though many children are being born in most families, not all children survive to be adults. The 19th century is a time of great inventions.

New ideas have made farming more efficient. Knowledge about hygiene spreads, vaccines are invented -- and fewer children die. Families still conceive many children -- and because fewer die, the families grow big: the population increases. At the beginning of the 20th century, many have moved to cities to work in factories. Children can get an education -- if the parents can afford it.

And women no longer work only in the home, they can have other occupations. Having many children is no longer an advantage -- families start shrinking in size. Now we have reached our time: contemporary Europe. Children attend school, most grown-ups have jobs, and the elderly can get a pension. And contraception has made it possible to plan the size of families.

Most families now, are small - with one or two children. And with good health care most people live longer. Now let's draw a diagram that shows how the birth rate and the death rate have changed. We divide the development into four steps -- four stages: In the first stage, many children were born but many also died: Both birth rate and death rate were high. In the second stage, the birth rate was still high.

But the death rate started declining. In the third stage, the birth rate started declining. And the death rate declined even more. In the fourth stage, both the birth rate and the death rate are equally low. Through the four stages, birth rates and death rates have gone down.

And in the phases were the birth rate is higher than the death rate, when more are being born than die, the population has increased. This is a model that shows how the population changes when many people become better off -- the demographic transition model. 'Transition' means change. The model describes what the progress has looked like in those countries that are rich today. But it can also be used to make forecasts for the future. Many populous countries, where incomes are low, are today in stage two, or three, during which the population still is increasing.

If they evolve according to the model - if more become better off - then Earth's population increase will eventually stop. But what happens in the countries that already are rich? Will they move into a new stage? Yes, some countries have started moving to a fifth stage, during which birth rates are so low that the population decreases. Well, we'll see if I'll ever have great-grandchildren.

Or great, great-grandchildren... or great, great, great...