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HPG - Demography Lesson

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Demography

Dynamics for Demographics

While an ecologist, studies population dynamics, such as changes in population size, within specific ecosystems, a demographer looks at the population dynamics specifically of the species Homo sapiens, or humans. Concepts of animal population dynamics can be applied to human population growth.

People of the World from 1000 AD to the Present day. Population compared - World, Africa, Asia, Europe, Latin America, Northern America.

Earth’s human population is multiplying rapidly, to the extent that some worry about the ability of the earth’s environment to sustain this population, as long-term exponential growth carries the potential risks of famine, disease, and large-scale death.

Demo-Graphy

Demography (demo- meaning the people & -graphy – measurement) is the statistical study of populations, especially human beings. Demographers study the historical size and makeup of the populations of countries to make comparisons and predictions. Also, demographers study properties that affect population growth, such as economics and social structure.

Developed Countries - Higher income, slower population growth VS Developing Countries - lower income, faster population growth

When studying populations and growth, countries are usually put in one of the following categories:

Developed countries

  • higher average incomes, slower population growth, diverse industrial economies, & stronger social support systems

Developing countries

  • lower average incomes, simple & agriculture-based economics, & rapid population growth

Ecologists look at many factors that help describe a population.  Click each of the images below to view the information.

Not only does demography take into account the birth rate and death rate, but also migration patterns.

Migration = Immigration + Emigration. Immigration - the number of people coming INTO a population. Emigration - the number of people EXITING a population.

 

Knowing the birth and death rates of populations gives information about a population’s health. For example, when a population is made up of mostly young organisms and the birth rate is high, the population is growing. A population with equal birth and death rates will remain the same size. Populations that are decreasing in size have a higher death rate than birth rate.

Birth rate + Death Rate + Migration = Population Size Birth rate - number of births within a population during a specific time period. Death Rate - number of deaths within a population during a specific time period. Migration - Immigration + Emigration. US Population as of 01/2019 = 328,277,44 Birth every 8 seconds Death every 11 seconds one international migrant every 34 seconds.

 

While the size of a population gives us information about right here and now, demographers are also concerned with how quickly the population is growing. Population growth rate (r) is how fast a population changes in size over time. A positive growth rate means a population is increasing. A negative growth rate means it is decreasing. The two main factors affecting population growth are the birth rate (b) and death rate (d). Population growth may also be affected by people coming into the population from somewhere else (immigration, i) or leaving the population for another area (emigration, e).

The formula for population growth takes all these factors into account.

r = (b + i) - (d + e) where r = the population growth rate. b = the birth rate. i = the immigration rate. d = the death rate. e = emigration rate.

 

Population Projections

Projections of population growth established in 2017 predict that the human population is likely to keep growing until 2100, reaching an estimated 8.6 billion in 2030, 9.8 billion in 2050 and 11.2 billion by 2100, while the 7 billion milestone was reached in 2011.

How do demographers study populations and make predictions about growth?

An important factor in population growth is the age-sex structure. This is the number of individuals of each sex and age in the population. The age-sex structure influences population growth because younger people are more likely to reproduce, while older people have higher rates of dying.

 World Population in Billions. Data from UN. 1800-2015 estimates. Shows growth scenarios through 2100.

 

The age-sex structure is represented by a population pyramid. This is a bar graph, like the one below. In this example, the bars become narrower from younger to older ages. Can you explain why?

Population Pyramid Births add individuals only to the base of the pyramid. Deaths remove individuals from the population at all ages after birth.

 There are less individuals in that age group!

There are 3 types of Population Pyramids.  Click on each for an example.

 Let's review with the video on Population Dynamics.

 

Demography Challenge

Before You Go, You Need To Know

The following key points are from this explore section of the lesson. You must know the following information before moving to the next lesson. This is just a summary of the key points.

  • Population growth rate is how fast a population changes in size over time.
  • Population growth is determined by rates of birth, death, immigration, and emigration.
  • The age-sex structure of a population is the number of individuals of each sex and age in the population.
  • Age-sex structure influences population growth. It is represented by a population pyramid.

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