Topic 2.3 Population Composition Vocabulary

Age Structures

• Age structures examine the proportion of the total population within each age group. These structures:
  • Vary based on the age distribution of individuals.
  • Vary by ethnicity.
  • Vary by socioeconomic status.
  • Are used to create population pyramids.

Sex Ratios

• Calculation:
  • Divide the number of male births by the number of female births.
  • Multiply the result by 100.
  • $\text{Sex Ratio} = \frac{\text{Number of Male Births}}{\text{Number of Female Births}} \times 100$
• Interpretation:
  • Ratio < 100: More female births than male births.
  • Ratio = 100: Male and female births are equal.
  • Ratio > 100: More male births than female births.
• Standard Biological Level: Approximately 105 male births to 100 female births.
• Patterns:
  • Sex ratios tend to be higher at younger ages.
  • Ratio differences decrease with age, often flipping by middle age.
• Factors Influencing Sex Ratios:
  • Sex-selective practices: sex-selective abortions, female infanticide, female child abandonment.
  • Variations by ethnicity.
  • Variations by economic status of a country.
  • Variations by socioeconomic status of a country.
• Examples:
  • China: 114 male babies to 100 female babies (due to the one-child policy).
  • India: 110 male babies to 100 female babies (preference for male babies for economic potential).
    • Note: This preference is connected to Unit 3 Culture.

Population Pyramids

• Also known as age-sex structures.
• Construction:
  • Horizontal axis: Sex or gender.
  • Vertical axis: Age cohorts (five-year groupings).
• Snapshot of demographics: Provides a view of whether a population is growing rapidly, slowly, or declining based on age and sex cohorts.
• Interpretation:
  • Wide base: High crude birth rates, rapidly growing population.
  • Narrower base (but still larger): Growing population, but crude birth rate is declining.
  • Widest middle: Growth is slowing.
  • Narrow, trophy-shaped pyramid with a large top cohort (80-85 range): High crude death rate and low crude birth rate, indicating a declining population.
• Scale:
  • Regional scale: Southern Asia (high crude birth rates, high number of people in childbearing years).
  • Country level: Finland (narrow base, wide middle, large top cohorts, aging and declining population).
  • Country level: United States (large cohort in the 50-59 range - Baby Boomers).

Practice Examples

• United States: Most people from 25 to 54, then a huge chunk at 65 and over.
• Uganda: Almost 50% of its population from 0 to 14 and another large cohort from 15 to 24 - high birth rate, huge amount in fertile years.
• Greece: Many people in the 65 and over range, rapidly aging population, crude birth rates are falling.

Real World Example: Rajasthan, India

• Problem: Possible underreporting of female births.
• Data: 2,456 male births and 2,102 female births.
• Calculation of Sex Ratio:
  • $\frac{2456}{2102} \times 100 = 117$
• Interpretation: 117 male births for every 100 female births.

Population Pyramids at Different Scales

• State Scale: West Virginia (high number of people from 55 and over, i.e., the Baby Boomer generation).
• County Scale: County in Colorado (low number of young people, high number of senior citizens; retirement communities).
  • Implication: If providing services to senior citizens (recreational or medical), target this area.
• City Scale: Salt Lake City Metropolitan Area (large cohort from 0 to 4, 5 to 9, up to the 20s, families with young children).

Conclusion

• Geographers can understand societies at various scales by looking at population composition.
• Analysis includes:
  • Whom is being counted.
  • What groups are being counted.
  • Grouping by age and sex.
• Informs:
  • Governments.
  • Retail.
  • Real estate sector.
• Geographers use the lens of the "why of where" by looking at the reasons behind the location decisions related to population pyramids and age-sex structures.