Demography Vocabulary Terms Regarding Population:
Births, Deaths, Migration

The following is a very basic and rudimentary listing of terms and expressions that are commonly used in the discipline of demography. This list is by no means a complete and exhaustive glossary of terms.

A personal note: The following terms and definitions are not the product of a trained demographer (I am a history major), and I am sure that a demographic specialist would take issue with some of my explanations. But for the most part, I have explained these terms with a lay audience in mind. I hope that this short glossary will be helpful for that limited goal.

Birth Rate: The ratio of the number of live births in a given period of time (usually a year) to the number of persons in a given population (the population number being calculated at some point in that year). Most birth rates are expressed in terms of births per 1000 people.

The birth rate can be found via the following basic equation: (Births divided by Population) x 1000

It can also be expressed as: (Births/Population) x 1000

Cohort: A group of people having some common feature who are measured in some fashion over a period of time

Crude Birth Rate: The ratio of the number of live births in a year (usually) to the total population of all males and females in a given population (a nation, state, etc.) per 1000 people. The crude birth rate can be found via the following equation:

(Births divided by the Total Population) x 1000 = Crude Birth Rate Bear in mind that the total population in calculating the crude birth

rate includes both males and females in the total population.

Crude Death Rate: The ratio of the number of deaths in a year to the
total population per 1000 people. In some instances, the crude death
rate is expressed per 100,000 people. For our purposes here, we will
usually express the death rate in terms of 1000 people. Also, the crude
death rate is sometimes called the crude mortality rate. The crude
death rate can be found via the following equation:

(Deaths divided by the Total Population) x 1000 = Crude Death Rate

Demographics: The statistical data derived from measuring human populations

Demography: The study and measurement of human populations through statistics

Emigration: The physical migration of a person or persons away from a given territory (perhaps a nation, a city, or some other community), and thus exiting the population of that territory

Fertility Rate: The ratio of all live births in a year (regardless of the age of the mother) to the sum total of all women of ages 15 to 44, the prime childbearing ages. The calculation of the fertility rate is found by dividing the total number of births by the population of women of ages 15 to 44.

Immigration: The physical migration of a person or persons into a given territory, and thus joining the population of that territory (perhaps a nation, a city, or some other community)

Migration: The physical movement of a person or persons either into a given physical territory, or away from a physical territory

Natural Decrease: A net negative population change in which the number of deaths in a population is greater than the number of births in a population in a given period of time (usually a year)

Natural Increase: A net positive population change in which the number of births in a population is greater than the number of deaths in a population in a given period of time (usually a year)

(Deaths divided by the Total Population) x 1000 = Crude Death Rate

Demographics: The statistical data derived from measuring human populations

Demography: The study and measurement of human populations through statistics

Emigration: The physical migration of a person or persons away from a given territory (perhaps a nation, a city, or some other community), and thus exiting the population of that territory

Fertility Rate: The ratio of all live births in a year (regardless of the age of the mother) to the sum total of all women of ages 15 to 44, the prime childbearing ages. The calculation of the fertility rate is found by dividing the total number of births by the population of women of ages 15 to 44.

Immigration: The physical migration of a person or persons into a given territory, and thus joining the population of that territory (perhaps a nation, a city, or some other community)

Migration: The physical movement of a person or persons either into a given physical territory, or away from a physical territory

Natural Decrease: A net negative population change in which the number of deaths in a population is greater than the number of births in a population in a given period of time (usually a year)

Natural Increase: A net positive population change in which the number of births in a population is greater than the number of deaths in a population in a given period of time (usually a year)

Net Migration: The mathematical difference between immigration and
emigration in a given territory in a given period of time (usually a year).

Net Migration can be expressed as: Immigration minus Emigration

Population: The total sum of persons in a given group. A population can be a wide variety of groups, large and small.

The largest human population, of course, is the sum total of all human beings who are currently alive. The United States, of course, has a total population, as does Baldwin County, Alabama. All American women from ages 15 to 44 make up another population. If fact, we consider these women to be a population in its prime childbearing years.

Population Change: The net amount of positive or negative change, in a given amount of time (often a year), to a given population. Population change can be either population growth (positive change) or population decline (negative change).

As an equation, population change can be expressed as:

(Births –Deaths) + (Immigration –Emigration) = Population Change.

Total Fertility Rate: A statistical scenario indicating how many live babies a woman would give birth to over the span of her reproductive years, a mathematical possibility based on the current age-specific fertility rates remaining constant throughout the course of a woman’s fertile years.

The calculation of the total fertility rate is a bit more complex than the formulas for the crude birth rate and the basic fertility rate. As such, the method for finding the TFR (total fertility rate) will be shown elsewhere.

But at this juncture it is important to note that when the TFR is higher than 2.0 (the possible number of children born to the average woman), the replacement rate either has been achieved, or perhaps has been achieved (depending on other factors like death rates, etc. in a territory).

In the United States, the replacement rate has been determined to be around 2.1, with the .1 being added for a variety of reasons like sex ratios and death rates. In some parts of the world, due to higher death rates, etc., the replacement rate is significantly higher than 2.1.

Net Migration can be expressed as: Immigration minus Emigration

Population: The total sum of persons in a given group. A population can be a wide variety of groups, large and small.

The largest human population, of course, is the sum total of all human beings who are currently alive. The United States, of course, has a total population, as does Baldwin County, Alabama. All American women from ages 15 to 44 make up another population. If fact, we consider these women to be a population in its prime childbearing years.

Population Change: The net amount of positive or negative change, in a given amount of time (often a year), to a given population. Population change can be either population growth (positive change) or population decline (negative change).

As an equation, population change can be expressed as:

(Births –Deaths) + (Immigration –Emigration) = Population Change.

Total Fertility Rate: A statistical scenario indicating how many live babies a woman would give birth to over the span of her reproductive years, a mathematical possibility based on the current age-specific fertility rates remaining constant throughout the course of a woman’s fertile years.

The calculation of the total fertility rate is a bit more complex than the formulas for the crude birth rate and the basic fertility rate. As such, the method for finding the TFR (total fertility rate) will be shown elsewhere.

But at this juncture it is important to note that when the TFR is higher than 2.0 (the possible number of children born to the average woman), the replacement rate either has been achieved, or perhaps has been achieved (depending on other factors like death rates, etc. in a territory).

In the United States, the replacement rate has been determined to be around 2.1, with the .1 being added for a variety of reasons like sex ratios and death rates. In some parts of the world, due to higher death rates, etc., the replacement rate is significantly higher than 2.1.

The TFR is a complicated statistical concept indicating a mathematical
possibility, not an actual event. Think of the replacement rate as the
sufficient level of births that could, in essence, replace the prior
parenting generation that produced the children.

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