POPULATION PYRAMIDS

POPULATION PYRAMIDS

1. Show the structure of a population by comparing relative numbers of people in different age groups

2. Population structures differ between LEDC and MEDC

3. POPULATION

   • World population Growth
     • until 1800 world population grew slowly for 1000,s years
     • 1820 world population reached 1 billion
     • early 1970,s world population reached 3 billion
     • 1999 less than 30 years later population doubled - 6 billion
     • Global rate is now 1 billion every 15 years
   • DEMOGRAPHIC TRANSITION MODEL
     • a measure of population change over time which tracks birth and death rates - shows population change over time. It studies how birth and death rate affect the total population of a country
     • 5 stages of demographic transition model
       • 1. Total population is low but balenced( BR = DR) due to high BR/DR
       • 2. Total population rises as DR fall due to improvements in health care and sanitation
       • 3. Total Population is still rising rapidly - gap between BR & DR narrows due to contraception - number of births exceed deaths
       • 4. Total population high but balanced by low BR & low DR
       • 5. Total population high but going into decline due to ageing population desire for small families and hving children later in life.
     • As populations move thru stages of the model gap between BR/DR 1st widens then narrows - stage 1 rates are balanced, stage 2 they move away from each other, stage 3 move towards each other, stage 4 balanced again

4. can be for town, are COUNTRY

5. LEFT HAND SIDE SHOW FIGURES FOR MEN RIGHT HAND SIDE FOR WOMEN

6. Shape can tell us alot - gives us information re BR/DR

   • shape which is triangular shows a population with high number of young dependants and a low life expectancy
   • Pyramid with fairly straight sides shows population with falling BR and rising life expectancy
   • Pyramid with upside down shape - has aging population with very low BR