Replacement Level: Definition & Overview

Lesson Transcript
Instructor: Sharon Linde

Sharon has an Masters of Science in Mathematics and a Masters in Education

Replacement rate is a number that relates to population replacement. How is this number calculated, and what does it mean? Read on for a better understanding of replacement rate and test your knowledge on fertility rates.

Fertility Rate

Before we get into replacement rate, it's important to fully understand fertility rate. Population scientists study fertility rate for a number of reasons, including predicting population growth or decline. Fertility rate is defined as the number of births per 1,000 women between the ages of 15-44 in a calendar year. Population scientists also look at total fertility rate.

Although they sound similar, fertility rate and total fertility rate are actually very different. Total fertility rate determines the number of children a hypothetical woman would have if she lived to be 44 years old. It also assumes that she has the exact same number of children in the future as women currently have. To show the vast difference between the two, the total fertility rate in the United States as of 2013 is just under 1.9 (babies); fertility rate is 62.5 (births). As you can see, those numbers differ greatly!

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Replacement Level

Now that we got that out of the way, let's dive into replacement level. Replacement level is the amount of fertility needed to keep the population the same from generation to generation. It refers to the total fertility rate that will result in a stable population without it increasing or decreasing. It is expressed as the total number of live births a woman would need to have over her child bearing years, which is typically ages 15-44.

In other words, scientists look at the population that is decreasing due to death or mobility and estimate the replacement rate, or the number of births necessary to replace the loss. They also look at the number of childbearing women and fertility rates in each group to determine replacement levels. This is why the number varies greatly from region to region; many of these factors change quite a bit over a period of time. While the replacement rate doesn't change drastically across a small region, it can show big changes across the globe.

This table shows current replacement rates for several regions:

Region Replacement Rate
Northern America 2.085
Europe 2.097
Oceania 2.176
Latin America/Caribbean 2.170
Central America 2.164
South America 2.166
Africa 2.699
Asia 2.320

The net reproduction rate is closely related to the replacement level but asks a slightly different question. It is defined as the average number of daughters a woman would have to bear to keep the population stable. This takes out the variation of gender births.

Factors That Affect Replacement Rate

Replacement rates can change over time. Let's discuss a few factors that can impact replacement rate.

  • Mortality rate is by far the most important factor. A higher death rate in an area would increase the replacement level for that region.
  • Immigration can also impact replacement levels. A population influx from elsewhere would decrease the replacement level.
  • In the same way, emigration, a population drain from an area, would increase the replacement level.
  • The gender ratio of births can have an impact on replacement rates. If a larger percentage of female are born than males, it will reduce the replacement level.

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Replacement Level: Definition & Overview Quiz

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What is the term for a sudden decrease in total fertility rates to replacement levels that could still result in a population increase for several generations?

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