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Population Growth

Population Growth

Author: Zach Lamb

Identify the determinants of population growth.

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Source: Intro Music by Mark Hannan; Public Domain

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[MUSIC PLAYING] Hello. Welcome to Sociological Studies. I hope you're having a great day. In this lesson, we're going to discuss population growth and the factors that affect population growth or population stability in the long term. Firstly, let's introduce demography. They are many social scientists who consider themselves to be demographers or who like to work with demography.

Demography is the empirical study of groups of people, of populations. So they'll be looking at characteristics of a population as a whole. It's a more quantitative way to look at the social world. Demographers are interested in population, things that affect population, and there's a formula we have for population. Population equals births minus deaths plus a variable for migration. So immigration minus emigration. Immigration people coming in to an area, to a country. And emigration is outflows of people. People going out of a country.

Demographers are interested in social variables, things that might affect birth rates-- education, job opportunities for women, the availability of contraceptives. These are social variables the affect things like birth rates. And obviously, the level of medical advancement might affect death rates as well. So there are many social variables that sociologists are interested in that affect these things in this equation. But this is the formula for population growth in society.

So let's break the formula down and look at its component parts. Let's look at some factors that might increase populations. Firstly, fertility. Fertility increases populations because fertility is the ability of an individual or a group, a population, to conceive children. So fertility then can increase population.

Birth rate. Birth rate is the rate of births over a specific time. Typically, births in a year. Births in a year per 1,000 people. For instance, if 100 babies are born in American society in 2012 per every 1,000 people in American society, that's a birth rate of 100 births per 1,000 so it's 10%. We'd have a birth rate of 10%.

Immigration, as I mentioned, a form of migration, which is the movement of people either into or out of a population. Immigration is the movement into a population and that can affect population as well. So now let's shift gears a little bit and let's look at factors that might decrease a population.

Mortality. We are mortal. Mortality is a measurement of how frequently death occurs within a population, as is the death rate. Which, just like the birth rate, is the measure of deaths over some period of time. Again, it's typically per 1,000 people. Infant mortality rate is a specific kind.

Infant mortality rate measures the rate of death for children that are under one-year-old. The United States does not have a very high infant mortality rate. Infant mortality rate, like these other variables, is related to societies. It's related to social progress and evolution.

Finally, emigration. The movement out of people in society. So adding it all together and then coming back to our formula, population equals number of births minus the number of deaths, so that'll give us one variable. Let's just call it one answer, so like a two. And then immigration minus emigration, so you have four people come in for every two people that leave. So that's two. So population is added in that way.

And finally, balancing everything, we have a measure of life expectancy. Life expectancy is just the average years to which somebody will live in society. And it varies by society and it varies between men and women. So for instance, in the United States, women have a longer life expectancy than men do by a few years. But this might be different in other societies as well. And life expectancy is a social variable. It's related to society and the level of social advancement.

So this has been just a descriptive overview of demography, of population, and the component parts that make up population growth or decline in society. Have a great rest of your day.

Terms to Know
Birth Rate

A rate of births over a specific time (normally expressed as x per 1,000 people).

Death Rate

A rate of deaths over a specific time (normally expressed as x per 1,000 people).


The empirical study involving the structure of human populations.


The ability to conceive children, which is measured statistically and referred to as birth rates.

Infant Mortality Rate

A rate of deaths of children under 1 year old over a specific time (normally expressed as x per 1,000 people).

Life Expectancy

The average years of life for a person within a group or population.


Movement of people into or out of an area.


Measuring how frequently death occurs in a given population.