A way of predicting population changes AGE STRUCTURE DIAGRAMS POPULATION STRUCTURE The population pyramid displays the age and sex structure of a country or given area Population in Five Year Age bands MALES To the left Usually, but not always, In % to make for easier comparisons between countries FEMALES To the right What Population Pyramids Show Us Economically More Developed Country Economically Less Developed Country KEY slope of pyramid indicate the death rate width of the base is related to birth rate/fertility rate proportions of men and women can suggest male or female migrations height of graph can indicate life expectancy (ignore the very thin end of the wedge as occurs on graph B as these people are a definite minority) "kinks" indicate dramatic reductions in birth rate or increases in death rate in the past area of graph indicates total population - compare areas of different population age groups or different sex on one graph The overall shape of the population pyramid can indicate whether it is an Economically More Developed Country or Economically Less Developed Country Population pyramid of a less developed nation (broad base population pyramid) Population Pyramid of Nigeria (1995) Importance of Population Pyramids A BROAD BASE POPULATION PYRAMID MEANS A COUNTRY SHOULD: •increase food production •build more homes & schools •plan for more job opportunities for the young in future •implement birth control program/campaigns •Usually agricultural population with problems of overpopulation. Population pyramid of a developed nation Population Pyramid of Sweden (1995) Importance of Population Pyramids A NARROW BASED POPULATION PYRAMID MEANS: Birth rate and Death rate low so a country may need to: •Work out incentives to encourage more births •Begin hiring foreign labor •Ensure proper medical services & health care for the aged Age Structure Diagrams Male Female Rapid Growth Guatemala Nigeria Saudi Arabia Ages 0-14 Slow Growth United States Australia Canada Ages 15-44 Zero Growth Spain Austria Greece Negative Growth Germany Bulgaria Sweden Ages 45-85+ Predict the future population change for each of the three age structure diagrams U.S. Population by age 1900, 2000, and 2050 projected Population structure by age and sex in developed and developing countries. Tracking the baby-boom generation in the U.S. THOMAS ROBERT MALTHUS 1766-1834 Growth Potential of Subsistence Vs. Population TIME 1 140 TIME 2 120 TIME 3 100 TIME 4 80 60 TIME 5 40 TME 7 20 TIME 6 0 SUBSISTENCE POPULATION TIME 7 Basic Point From MALTHUS: Population and food supply (subsistence) grow at different rates Population will outgrow food supply Results from the point of crisis include famine and war What are advantages and disadvantages of reducing births: Controversy Can the world’s resources support an additional 2.5 billion by 2050? Is the Earth overpopulated? Carrying capacity If yes, what should be done? What is a sustainable population?