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Valerie holds a Ph.D. in Health Psychology.
'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.
A typical measurement used for fertility is the crude birth rate, which is the number of live births in a given year for every 1,000 people in a population. In order to determine a population's fertility rate, demographers use governmental records to figure out the crude birth rate. Demographers calculate the crude birth rate by dividing the number of live births in a year by the total population and then multiplying the result by 1,000. For example, in the year 2000, 327,882 live births occurred in Canada (population 30 million) for a crude birth rate of 10.9. The term 'crude' relates to the fact that comparing such rates can be misleading because it doesn't focus on women of childbearing age and it doesn't consider varying rates between racial, ethnic, and religious groups. It is, however, easy to calculate and provides a measure of a society's overall fertility.
The death rate is known as mortality. Mortality also influences a population's size and is defined as the number of deaths in a society's population. Mortality is calculated much like how the crude birth rate is calculated. Demographers calculate the crude death rate as the number of deaths annually per 1,000 people in a population. Demographers calculate this figure by dividing the number of deaths in a year by the total population and then multiplying the result by 1,000. The crude death rate in the United States normally stays around 8 or 9.
Infant mortality occurs when a child dies after birth. Childhood mortality is the death of a child before their fifth birthday. The infant mortality rate is the number of deaths among infants under age 1 for each 1,000 live births in a year. Ninety-nine percent of these infant and childhood deaths occur in developing nations. Generally the most common cause worldwide was dehydration from diarrhea. Many factors contribute to infant mortality such as the mother's level of education, environmental conditions, and political and medical infrastructure.
Demography is interested in changes in human populations; demographers focus on specific indicators of change. Two of the most important indicators are birth and death rates, which are also referred to as fertility and mortality. Mortality refers to the finite nature of humanity: people die. Mortality in demography is interested in the proportion of deaths in relation to the population. Fertility, on the other hand, affects the population by the number of children that a woman bears during her reproductive years.
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