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Population Basics Demographics

Population Basics Demographics. In order to save this file to the website, many visual illustrations had to be eliminated to reduce the file size. Part I: Population Distributions. Distribution : describes the locations on the Earth’s surface where individuals or groups live.

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Population Basics Demographics

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  1. Population BasicsDemographics In order to save this file to the website, many visual illustrations had to be eliminated to reduce the file size.

  2. Part I: Population Distributions Distribution: describes the locations on the Earth’s surface where individuals or groups live.

  3. Distribution of Population • World population is most dense in 4 regions: • East Asia • South Asia • Southeast Asia • Western Europe

  4. Sparsely Populated Areas • Wet Lands • Dry Lands • Cold Lands • High Lands

  5. Ecumene The portion of the earth with permanent human settlement, has expanded to cover most of the world’s land area.

  6. Ecumene Over Time

  7. Part II Population Density • Density is a measurement of the number of people per unit area; such as a square kilometer or square mile. • How is Density different from Distribution?

  8. Types of Density • Arithmetic Population Density: the total number of people per a unit of land area. • Physiological Density: the total number of people per a unit of arable (farmable) land. • Agricultural Density: The total rural population / amount of agricultural land.

  9. Part II: Measures of Population ChangePopulation Change refers to any given shift in the overall makeup of a given population usually referring to either positive population growthor negative population growth

  10. Major Population Measures • Crude Birth Rate (CBR) • Crude Death Rate (CDR) • Natural Increase Rate (NIR) • Total Fertility Rate (TFR) • Infant Mortality Rate (IMR)

  11. Population Measures • Crude Birth Rate • Total number of births in a year for every 1,000 people alive in a society • Crude Death Rate • Total number of deaths in a year for every 1,000 people alive in a society

  12. Natural Increase Rate • The percentage growth of a population in a year, computed as the crude birth rate minus the crude death rate • The world’s NIR is about 1.3 percent or 80 million people per year • At current rates the world population will double again in 54 years Doubling Time • Almost all of the world’s natural increase is centered in less developed countries • What parts of the world are growing most quickly? Slowly?

  13. Fertility • Total Fertility Rate (TFR) is used to measure the number of births in a society. • This is the average number of births a woman will have through her child-bearing years (15 through 49) • The average world TFR is 3, though it exceeds six in some African countries and is less than 2 in Europe Replacement Rate

  14. Infant Mortality • Infant Mortality Rate (IMR) is the annual number of deaths of infants under one year of age compared to total live births per 1000. • Life expectancy measures the number of years a newborn child can expect to live • Babies born today in Western Europe can be expected to live into their late 70’s, early 30’s in Africa • CBR, NIR, TFR and IMR can all be used as predictors of a country’s development

  15. Calculating Infant Mortality Survivorship curves keep track of the fate of any given birth cohort. They show the percent still living at a given age. Upper curve: Late 20th.C. developed country. Middle Curve: 19th. C. developed country/20th.C. less developed country. Lower Curve: City of York (England), 16-17th.C.

  16. Illustrating Population • Population Pyramid: A bar chart that shows the age and sex distribution of members of a  population. The age divisions are referred to as "cohorts" and may be in 5 or 10 year increments, depending on the level of detail desired. By convention, females are always plotted to the right, males to the left. The units across the base may be either absolute numbers or percent of the population.

  17. Illustrating Population Change over Time: The Demographic Transition Model • The "Demographic Transition" is a model that describes population change over time. It  is based on an interpretation begun in 1929 by the American demographer Warren Thompson, of the observed changes, or transitions, in birth and death rates in industrialized societies over the past two hundred years or so. • By "model" we mean that it is an idealized, composite picture of population change in these countries. The model is a generalization that applies to these countries as a group and may not accurately describe all individual cases. Whether or not it applies to less developed societies today remains to be seen.

  18. STAGE ONE  is associated with pre Modern times, and is characterized by a balance between birth rates and death rates. This situation was true of all human populations up until the late 18th.C. when the balance was broken in western Europe. • Note that, in this stage, birth and death rates are both very high (30-50 per thousand). Their approximate balance results in only very slow population growth. Over much of pre-history, at least since the "Agricultural Revolution" 10,000 years ago, population growth was extremely slow. Growth rates would have been less than 0.05%, resulting in long doubling times of the order of 1-5,000 yrs.

  19. STAGE TWO sees a rise in population caused by a decline in the death rate while the birth rate remains high, or perhaps even rises slightly. The decline in the death rate in Europe began in the late 18th.C. in northwestern Europe and spread over the next 100 years to the south end east. The decline in the death rate is due initially to two factors: improvements in food supply and significant improvements in public health that reduced mortality, particularly in childhood

  20. STAGE THREE  moves the population towards stability through a decline in the birth rate. This shift belies Malthus's belief that changes in the death rates were the primary cause of population change.

  21. STAGE FOUR is characterized by stability. In this stage the population age structure has become older:

  22. A Population at Stage 4 Birth Rate: 12 per thousand Total fertility rate: 1.8 births Natural increase: 0.1% per year 1990-2000 Age structure: 18% under 15 yrs.age

  23. Extreme Stage 4In some cases the fertility rate falls well below replacement and population decline sets in rapidly: Birth Rate: 9 per thousand Total fertility rate: 1.2 births Natural increase: -0.1% per year 1990-2000 Age structure: 14% under 15 yrs.age

  24. Population Momentum • Population momentum refers to the  tendency for population growth to continue beyond the time that replacement-level fertility has been achieved because of a highly relatively high concentration of people in the childbearing years. • Look at the following pop. pyramids of India at three different time periods and note the changes.

  25. By using these concepts we can then explain the differences we see in population growth rates across the world today:

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