# What is fertility rate? Definition and examples

Fertility rate is the average number of babies born to females during their reproductive years. In other words, the total number of children that would be born to each human female if she lived to the end of her child-bearing years. We get a country’s fertility rate by summing the single-year age-specific rates at a given time.

We can also use the terms total fertility rate (TFR) and absolute/potential natality.

TFR is the single most important factor in any country’s population growth. Another factor is, for example, in the advanced economies, immigration.

Life expectancy is also a factor that influences a country’s total population. In this context, life expectancy refers to how long we expect the people in a country or area to live.

By the end of this century, the global fertility rate will have declined considerably. (Data Source: United Nations)

## Ideal fertility rate

For a country to maintain its population, women, on average, should have 2.1 children. Those children should survive to at least the age of fifteen.

The figure of 2.1 children assumes that there is no emigration or immigration.

The United States, United Kingdom, and other advanced economies can maintain their populations with relatively low TFRs. This is because they have high levels of immigration, i.e., many people come from abroad to live there permanently.

According to Britannica.com:

” average number of children born to women during their reproductive years.”

“For the population in a given area to remain stable, an overall total fertility rate of 2.1 is needed, assuming no immigration or emigration occurs.”

## Birth vs. fertility rate

Do not confuse birth rates with fertility rates. Many online dictionaries explain birth rate with the same meaning as fertility rate – this is a mistake!

##### Birth Rate

Birth rate is the number of live births per 1,000 women in the total population. We usually calculate this figure on an annual basis.

In 2016, the average birth rate globally was 18.5 births per 1,000 total population.

If a country has a very low birth rate, it has to deal with an aging population, i.e., a growing proportion of elderly people. Japan has the world’s lowest birth rate.

##### Fertility rate

TFR is the average number of babies that would be born to a woman during her fertile years. In other words, the number of babies, on average, born to women aged between about 15 and 49.

The rate only includes women who survive at least through the end of their reproductive lives.

## Video – the fertility rate

This Project M video explains why predicting the future population of the world is not that easy.