APES 3.6 Age Structure Diagrams

Population Pyramid

  • The age structure diagram is like a population pyramid you may have seen in other classes
  • It shows the distribution of ages and genders in a certain population
  • Not always pyramidal
  • The x-axis shows the number of individuals
  • The y-axis, usually in the middle dividing male and female, shows age groups
    • Age groups are divided by reproductive ability
    • Pre-reproductive: 1-14 years old
    • Reproductive: 15-45 years old
    • Post-reproductive: 46-100+
    • This is in humans and is a huge generalization
    • Different species have different reproductive ages

Shapes and Meanings

  • Bottom heavy pyramids indicate that the population is mainly young and growing quickly
    • Younger age groups make up a majority of the population
    • They will be reproducing longer
    • In humans, this usually indicates a developing nation
  • Middle heavy or triangular pyramids mean population growth is stable
    • All reproductive age groups have similar percentages
    • Not as many younger groups will be moving into reproductive stages soon
    • Nations in this stage are developed
  • Top heavy pyramids indicate that the population is declining
    • The largest percentage of the population is past reproductive age
    • Economically and socially developed
    • Higher levels of education are common
    • Long-term services may be impacted
    • They may not be enough people employed in healthcare to care for so many dependents