1. Components of Population Growth
Crude Birth Rate (CBR)
Crude Death Rate (CDR)
Natural Increase Rate (NIR or RNI)
Total Fertility Rate (TFR)
Infant Mortality Rate (IMR)

2. Crude Birth Rate
Total number of live births in a year for every 1,000 people alive in the society.
United States = 13
Niger = 50

3. Crude Death Rate
Total number of deaths in a year for every 1,000 people alive in a society.
U.S. = 9
Niger = 11

4. Natural Increase Rate (NIR) or Rate of Natural Increase (RNI)
The percentage by which population grows in a year. Compute by subtracting CDR from CBR. Natural means births, this excludes migration.

5. Total Fertility Rate
The average number of children a woman will have in her childbearing years (15-45).

6. Infant Mortality Rate
The number of deaths under one year of age occurring among the live births in a given year, per 1,000 live births occurring among the population.

8. Population Pyramids

9. Key Terms Population Pyramid Dependency Ratio Age Distribution
Sex Ratio

10. Key Terms Defined
Population Pyramid: A bar graph representing the distribution of population by age and sex
Dependency Ratio: The number of people under the age of 15 and over age 64 compared to the number of people active in the work force
Age Distribution: The percentage of the population within a country in each age group (broken down into 5-year intervals)
Sex Ratio: The number of males per 100 females in the population

11. How it works… Males on the left, females on the right
Youngest on the bottom (0-4), oldest on the top (100+)
Generally done as a percentage of the population, sometimes as total numbers
Shape of the pyramid is generally shaped by the CBR in a country

12. Pyramid for Stage 1 Wide base = very high birth rate
Narrows very quickly = high death rate
Very few reach old age

13. Pyramid for Stage 2 Wide base = High birth rate
Wider & taller = people living longer

14. Pyramid for Stage 3 “Domed” shape = more people living to be older
Proportionately fewer births

15. Pyramid for Stage 4 Small base, small top Bulge in the middle
CBR and CDR are low.
Population is stagnant

16. All four Stages
Convex Profile
Concave Profile

18. Effects of Population Growth
Rapid Growth (stage 2)
Need services for children
Fewer old people = less money spent on them
People move to cities to find work
Countries with the fastest growth have the fastest growing cities
Quickly constructed buildings to house workers
Often lack vital services (water, electricity, sanitation)
Some migrate to more developed countries
Slow Growth (stage 4)
Need services for elderly
Fewer young people = less money spent on them
Could be shortage of workers in the future
Migrants move into the country, often to work in low wage jobs that would be otherwise hard to find workers

20. Outside Influences Migration: young males are more likely to migrate
Famines: can cause a clear drop in population, especially among the very young
War: clear drop in male populations of fighting age

21. Why?
We can gain a lot of information about a city, nation, region, etc. by looking at a population pyramid.

22. Age
Lawrence, KS (College town)
Naples, FL (42% over age 65)

23. Gender
Unalaska, AK (Military Base)