Thursday, 2 June 2016

Population pyramids


A population pyramid is a type of bar graph used to show the age and gender structure of a country, city or other area. The horizontal axis is divided into either numbers or percentages of the population. The vertical axis shows age categories. 

Stage 1 population pyramids:



  • Wide base due to extremely high birth rate 
  • Infant and child mortality rates are high, so the sides of the pyramid curve in quickly 
  • Death rate is high in all age groups, so life expectancy is low
  • Very narrow apex and the shortest of all the pyramids 
Stage 2 population pyramids:
  • Sides slightly less concave due to decrease in death rate 
  • Few more elderly people in population shown by apex 
  • Base narrower due to slight decrease in birth rate
Stage 3 population pyramids: 
  • Narrowing base shows decrease in birth rate
  • Sides straighter as more people live into old age due to health improvements 
Stage 4 population pyramids:
  • Straight sides show steady birth rate
  • Concave shape shows birth rate reducing 
  • Life expectancy high - most people die in old age 
Stage 5 population pyramids:
  • Increasing proportions in the very elderly group
  • Middle aged generations much larger than those of children because of low birth rate 
How can a population become sustainable? 

A sustainable population is one whose growth and development is at a rate that does not threaten the success of future generations. 
Most sustainable = stage 4 countries. 

Why are stage 5 populations not sustainable? 

Stage 5 populations are not sustainable because numbers are decreasing. If the population continues to decrease, the country will die out. 

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