Demographic Changes from Fertility and Birthrates

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  • 0:05 Population
  • 0:57 Demography
  • 2:21 Fertility
  • 3:56 Crude Birth Rate
  • 5:01 Mortality
  • 6:23 Lesson Summary
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Lesson Transcript
Instructor: Valerie Houghton, Ph.D.

Valerie holds a Ph.D. in Health Psychology.

Demographers focus on specific indicators of change in human populations. Two of the most important indicators are birth and death rates, or fertility and mortality. In this lesson, we will discuss the definitions of demography, fertility and mortality and their impact on a population.


'Observations Concerning the Increase of Mankind, Peopling of Countries, etc.' is a short essay written in 1751 by Benjamin Franklin. Writing as, at the time, a loyal subject of the British Empire, Franklin argues that the British should increase their population and power by expanding across the Americas, taking the view that Europe is too crowded. Well, that is exactly what happened as 60 million people left Europe and migrated to the United States between 1815 and 1932. This influx of immigrants impacted the population of the United States in many ways. In order to understand some of the ways a population can change, in this lesson we will discuss the definitions of demography, fertility, and mortality, and their impact on a population.


In the early 17th century, the population of the British colonies increased from several hundred individuals to about 2.5 million in 1780. Today Franklin's essay is remembered as an influential precursor of the Malthusian theory. Thomas Robert Malthus (1766-1834), English economist and clergyman, argued that increases in population, if left unchecked, would eventually result in social chaos. Malthus predicted that the human population would continue to increase exponentially (1, 2, 4, 16, 256...) until the situation is out of control. He also warned that food production would only increase arithmetically (1, 2, 3, 4, 5...) because of the limitations in available farmland.

To say the least, Malthus provided a disturbing vision of the future that included massive global starvation as a consequence of unrestrained population growth. From the observations of population growth made by Franklin, Malthus, and others, the field of demography arose two centuries ago. Demography, from the Greek word meaning description of people, is the study of human population, while a person who studies the human population is known as a demographer. A demographer is actually considered a social scientist who analyzes the causes and effects of population changes.


A population can change based upon people migrating into an area or out of an area, but a population can also change based upon how many people are being born, how many people are capable of having children, and how many people are dying. A population's size is first affected by fertility. Fertility is the number of children that an average woman bears during her reproductive years. A female's childbearing years last from the beginning of menstruation to menopause. Fertility depends on many factors such as nutrition, sexual behavior, culture, endocrinology, economics, lifestyle, and emotions.

The term fertility is often confused with the term fecundity, but they are not the same thing. Fecundity is the number of children an average woman is capable of bearing. The number of potential children a woman can have is often reduced by health, financial constraints, cultural norms, and personal choice. For example, as of 2012 the world's average fertility rate is about 3 children per woman, while its fecundity rate is about 20 per woman. The highest fertility rate occurs in Africa where the average fertility rate is about 6. On the other hand, Europe has the lowest fertility rate where each woman has, on average, 1 child. In the United States, the average fertility rate is about 2.

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