How Total Fertility Rate Affects a Country's Population

Multi Ethnic Babies Sitting on White.
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The term "total fertility rate" describes the total number of children the average women in a population is likely to have based on current birth rates throughout her life. The number ranges from more than six children per woman in developing countries in Africa to around one child per woman in Eastern European and highly developed Asian countries.

Replacement Rate

The concept of replacement rate is associated with total fertility rate. The replacement rate is the number of children each woman needs to have to maintain current population levels, or what is known as zero population growth, for her and the father. 

In developed countries, the necessary replacement rate is about 2.1. Since replacement cannot occur if a child does not grow to maturity and have their own offspring, the need for the extra 0.1 child (a 5 percent buffer) per woman is due to the potential for death and factors in those who choose or are unable to have children. In less developed countries, the replacement rate is around 2.3 because of higher childhood and adult death rates.

World Fertility Rates Vary Widely

Nonetheless, with total fertility rates of 6.01 in Mali and 6.49 in Niger (as of 2017), the resultant growth in these countries' populations is expected to be phenomenal over the next few years, unless growth rates and total fertility rates drop. For example, Mali's 2017 population was approximately 18.5 million, up from 12 million a decade prior. If Mali's high total fertility rate per woman continues, the population will continue to explode. Mali's 2017 growth rate of 3.02 means a doubling time of just 23 years. Other countries with high total fertility rates included Angola at 6.16, Somalia at 5.8, Zambia at 5.63, Malawi at 5.49, Afghanistan at 5.12, and Mozambique at 5.08.

On the other hand, more than 70 countries had (as of 2017) a total fertility rate of less than 2. Without immigration or an increase in total fertility rates, all of these countries will have declining populations over the next few decades. Some of the lowest total fertility rates included developed as well as developing countries. Examples of countries with low fertility rates were Singapore at 0.83, Macau at 0.95, Lithuania at 1.59, the Czech Republic at 1.45, Japan at 1.41, and  Canada at 1.6.

The U.S. Fertility Rate Is Below Replacement

The total fertility rate for the United States in 2017 was below replacement value at 1.87 and the total fertility rate for the world was 2.5, down from 2.8 in 2002 and 5.0 in 1965. China's one-child policy definitely shows in the country's total low fertility rate of 1.6.

Different cultural groups within a country can exhibit different total fertility rates. In the United States, for example, when the country's total fertility rate was 1.82 (in 2016), the total fertility rate was 2.09 for Hispanics, 1.83 for African Americans, 1.69 for Asians, and 1.72 for whites, still the largest ethnic group.

Total fertility rates are closely tied to growth rates for countries and can be an excellent indicator of future population growth or decline for a country or for a population within a country.