Population pyramids provide 3 types of information: 1) The age and gender distribution of a population shown in bars representing 5-year increments, 2) The dependency ratio calculated from the elderly and child populations, and 3) The stage of demographic transition based on birth and death rates. Demographic transition models population growth through 4 stages from high birth/death rates to low growth as societies develop.

1. Population Pyramids by Gayle Robinson http://orru.latervista.org

2. Population Pyramids Provide 3 types of information : Age/gender distribution Dependency ratio Demographic Transition position

3. Age/Gender Distribution Each bar represents a 5-year increment beginning at 0. Males are shown on the left. Females are shown on the right.

4. Dependency Ratio Elderly population 65+ years of age Children 0-14 years of age Workforce

5. The Demographic Transition Model Low Growth High growth Moderate Growth Low Growth http://www.uwmc.uwc.edu/geography/Demotrans/demtran.htm Population Pyramid Shape

6. Stage 1: Low Growth No country in Stage 1 today High Crude Birth and Death Rates

7. Stage 2: High Growth Large base with high CBR Developed world entered this stage during Industrial Revolution Increased Life Expectancy Decreased CDR Fig. 2-16: Population pyramids can vary greatly, with different fertility rates (Laredo vs. Honolulu), or among military bases (Unalaska), college towns (Lawrence), and retirement communities (Naples).

8. Stage 3: Moderate Growth CBR decreases through societal changes CDR continues to decrease Fig. 2-17: Cape Verde, which entered stage 2 of the demographic transition in about 1950, is experiencing rapid population growth. Its population history reflects the impacts of famines and out-migration.

9. Stage 4: Low Growth Smaller base with decreased CBR Larger number of elderly population Can become top-heavy with decreased CBR Fig. 2-18: Chile entered stage 2 of the demographic transition in the 1930s, and it entered stage 3 in the 1960s.