Last lesson you measured two populations and found that Niger would double in a little over twenty years, while Switzerland, left to its births and deaths alone, would take a thousand. You also found that almost all of Switzerland's growth comes from migration rather than from natural increase.
That leaves an obvious question. If a human population is a system with four flows running through it, can a government reach in and change one of them?
Governments certainly try. Some pay people to have children. Some have paid people not to. Some open or close the door to migrants. Others change nothing about births at all, build schools and clinics instead, and watch the birth rate fall anyway. Today you will look at how well each of those works, and you will start with the reason anyone bothers: nobody is certain how many of us there will be by the end of this century.
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8.1.4 The global human population has followed a rapid growth curve. Models are used to predict the growth of the future global human population.
UN projection models indicate three scenarios linked to future fertility rates. There is uncertainty about how future human fertility rates may change, leading to the three scenarios in the models.
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In the last lesson you watched a counter climb from early human history to the present, and you described what happened to the speed of growth. For almost all of human history that line is close to flat. It bends sharply upwards only in the last two centuries. That shape has a name: a rapid growth curve.
Here is where the curve has reached. The United Nations put the world population at 8.2 billion in 2024. The global total fertility rate, which you met in 1.1, now stands at 2.25 births per woman, down from 3.31 in 1990. More than half of all countries and areas are already below the replacement level of 2.1, and two thirds of people alive today live in one of them.
That last figure is the one that surprises people. The population is still growing, but the input driving the growth has been weakening for decades.
So what happens next? Nobody knows, and the honest way to say so is with a population projection: a model that takes what we know about current births, deaths and migration and runs it forward under stated assumptions. The UN publishes three, and what separates them is almost entirely an assumption about future fertility.
Under the medium scenario the world population reaches a peak of around 10.3 billion in the mid-2080s, then falls back to about 10.2 billion by 2100. The UN puts the likelihood that the population peaks at some point this century at 80 per cent.
Notice what the three scenarios do not disagree about. Deaths are reasonably predictable, because life expectancy changes slowly and in a fairly steady direction. Fertility is not, because it depends on decisions that hundreds of millions of people have not made yet. That is exactly the thing a model cannot know, so the UN gives you a range instead of pretending otherwise.
Which brings us to the rest of the lesson. If the difference between 10 billion and something rather larger comes down to fertility, and fertility comes down to decisions, it is not surprising that governments have tried to influence those decisions.
United Nations, DESA, Population Division. World Population Prospects 2024. Licensed under CC BY 3.0 IGO
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8.1.5 Population and migration policies can be employed to directly manage growth rates of human populations.
These may be anti-natalist or pro-natalist, thereby directly addressing birth rates, or they may address immigration and emigration. These policies may use a variety of cultural, religious, economic, social and political factors to achieve their aims. Include named examples.
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A population policy is a deliberate attempt by a government to change the size or the growth rate of its population. Population policies sort by the flow they aim at.
What makes all three direct is that changing the population is the stated point of them. When a government raises child benefit in order to raise the birth rate, the population is the target, not a side effect.
Governments pull whatever levers they have. Policies work through cultural, religious, economic, social and political means, and most use several at once:
Two things to hold on to before the examples. First, a policy aimed at births is aimed at decisions people make about their own bodies and families, which gives these policies an ethical weight that a policy about, say, waste collection does not carry. Second, a policy that has been announced is not the same as a policy that works. Telling those two apart needs evidence, and that is what the next two examples are for.
The situation. In 2025 Japan recorded 671,236 births, the lowest number since national records began, and a total fertility rate of 1.14, also a record low. In the same year there were 1,589,489 deaths. Deaths outnumbered births by 918,253, the nineteenth year in a row in which Japan's population has fallen through natural change alone.
The direct pro-natalist policy. In December 2023 the Japanese Cabinet adopted the Children's Future Strategy, raising annual spending on children and child-rearing by 3.6 trillion yen. Its measures are direct payments and direct entitlements:
Source: Children's Future Strategy, Cabinet decision of December 2023, Children and Families Agency.
The other door. While births fell, Japan's population of registered foreign residents passed 4 million for the first time, reaching 4,125,395 at the end of 2025, an increase of 356,418 people, or 9.5 per cent, in a single year. Deciding who may come to live and work in the country is a migration policy, and it is every bit as direct a population policy as the child allowance is.
One caution about that second figure, and it matters. 4,125,395 is a count of people on a register, not a measure of net migration. It rises when someone arrives, and it also rises when someone already in Japan changes their status, and it falls when people leave or naturalise. You met the same problem in 1.1, where the country profiles gave you net migration and would not give you immigration and emigration separately. Use the figure for what it is.
Working out what a figure actually measures, before you build an argument on it, is a skill you will use every time you take data from someone else, including in your own investigation.
Births, deaths and natural change: Ministry of Health, Labour and Welfare, 2025 demographic statistics. Registered foreign residents: Immigration Services Agency.