Natural Increase

Do you ever think about how the number of people born and the number of people that die might affect how the overall world population changes? When there are more births than deaths globally, the population will have a natural increase. When the opposite occurs, and there are a higher proportion of deaths to births, a natural decrease will take place. But how do we define these ideas exactly? Is there a specific calculation? Let's find out.

Natural Increase Definition

Natural increase considers the natural changes in a population as a result of changing birth rates and death rates. Let's define these terms.

When birth rates outweigh the death rates, a natural increase in population will occur.

Notably, the natural increase does not include migration statistics (neither emigration nor immigration). Combining migration statistics with natural increase statistics can provide the total population change or population growth rate. Keeping these figures separate can reveal which form of population increase is having a greater impact on an area's population growth or decline.

Natural Increase Calculation

The rate of natural increase is the actual number (usually written as a percentage) that illustrates the natural increase in an area over time given a set population. The natural increase calculation is not as difficult as you might expect. Let's take a look at the formula.

(Number of births - number of deaths) ÷ population = rate of natural increase

Natural Population Growth

Purely by the definition of natural increase, there is only one way for natural population growth to occur. People being born. Although migration is a natural activity (humans and other animals have been doing it since time immemorial), this is little more than a matter of semantics. Birth and death are 'natural,' while migration is not. Governments may want to encourage natural increase (births) while discouraging migration, or vice versa, or neither, or both. We'll explore the 'whys' and 'hows' of natural increase a little later.

Natural Decrease Definition

A natural decrease occurs when the number of deaths is higher than the number of births. Revisiting Sailor Town, suppose the number of births was 250 while the number of deaths was 500. That would make the rate of natural increase -2.5% rather than 2.5%. So, a natural decrease.

If both the rate of natural increase and the migration rate are negative, then a population will experience negative population growth, i.e., the population will shrink over the course of the year. This situation is most common within countries on two opposite ends of the spectrum: highly developed countries and disaster-stricken countries.

In developed countries, citizens may be less interested in having children for social, cultural, or economic reasons, resulting in negative population growth – especially if said country also has strict immigration laws (think Japan). On the other hand, a major disaster in a country may prompt involuntary mass migration, with those who stay behind unwilling or unable to have children. Depending upon the nature of the disaster, the death rate may far outweigh the birth rate.

Most governments try to avoid a natural decrease; an increasing population (whether via natural increase or immigration) can feed into the labour force and tax base, allowing a government to expand its capabilities both internally and on the world stage. There are exceptions, of course. Some governments find that their capacities are stretched too thin with an ever-increasing population, and so seek to actually encourage a natural decrease or even restrict immigration.

Reasons for Natural Increase

There are many different reasons for natural increase (and natural decrease). Let's take a look at a few.

Public policies

Pronatalist policies are public policies that encourage or enable citizens to have children, while antinatalist policies are policies that encourage citizens to have few or no children.

Theoretically, a government that exclusively supported pronatalism would not care about the circumstances of natural increase, only that the natural increase was occurring – even if the new parents lacked the responsibility or ability to take care of their children. Therefore, untempered pronatalism is rare, and sometimes, governments may support some pronatalist and antinatalist policies at the same time.

Social factors

The birth rate is influenced by more than just the policies and 'decrees' of a government. We mentioned earlier that the birth rate may decline when a country becomes highly developed or if a country is experiencing a disaster. But citizens may be inclined to have more children due to cultural or economic reasons. The Catholic Church, for example, teaches that sexual intercourse is only meant for procreation and that contraception is wrong (though many Catholics disregard this). In more conservative Catholic areas, this can cause quite a significant rate of natural increase. Similarly, agricultural communities, especially those practising crop-based intensive farming without mechanization or agrochemicals, may be inclined to have more children so that they get 'free labour' to help around the farm.

Death rate

It's important to consider the effect that the death rate has on the natural increase as well. It's not just all down to the birth rate. If a community, city, state, or country had an astronomical birth rate but was being outpaced by the death rate, it would still result in a natural decrease. Things like high-quality healthcare and medicine, balanced diets, and assisted living arrangements can help senior citizens live longer, while traffic safety, law enforcement, and firefighting can reduce deaths in general, decreasing the death rate. A lower death rate and a higher birth rate will result in a greater rate of natural increase.

World Rate of Natural Increase

When we take the entire globe into account, migration isn't relevant. Therefore, the world rate of natural increase is more or less the rate at which the entire human population is growing each year.

In November 2022, the human population reached 8 billion people. However, despite this, the rate of natural increase is actually slowly decreasing. Population growth may stall and eventually begin to decrease (though that may not happen until we add a few more billion people).

Fig. 1 - Global rate of natural population increase, 1950-2021.

According to the graph above, in 2021, the world rate of natural increase was 0.82%. By comparison, in 1963, the world rate of increase was 2.27%. This shows that the world rate of natural increase has actually gone down, albeit slowly.

Typically, high natural increase rates are found in developing world countries. As of 2021, Niger, one of the poorest countries globally, sits at the top of the leaderboard for natural increase. Much of Central Africa also has high natural increase rates, at 3% or above. Interestingly, much of Europe, Russia, Japan, South Korea, and some South American countries are below 0%, meaning they have a negative natural increase.

Fig. 2 - map of the global rate of natural population increase in 2021

UK Natural Increase

Let's hone in on the United Kingdom's natural increase specifically. In 2021, the UK's rate of natural increase was 0.04%, meaning that the birth rate was barely above the death rate. By comparison, in 1950, the UK's rate of natural increase was 0.47%. Just like the rest of the world, the UK's natural increase rate is decreasing.

Fig. 3 - the rate of natural population increase in the United Kingdom, 1950-2021.

This is a result of lower fertility rates, as well as better access to contraception. Also, the high cost of living tends to deter people from having children earlier. Much of the population growth in the UK is actually a result of increased immigration. Now that Brexit is in full force, it will be interesting to see the change this will make.

If fertility rates remain low in the UK, and people continue to die (either an increase or remain stable), the overall natural increase will go down even further or may flip entirely into the minuses, with a negative natural increase. This may mean that immigration may become the only way that the population can be stable in the UK; an interesting Brexit debate for the future. If natural increase and immigration fall into negative figures, the UK could go into serious population decline.