APES 3.6 Age Structure Diagrams

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

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