1. Population Dynamics
Lecture II

2. Population Change Occurs by:
Births
Deaths
Immigration
Emigration
We will focus on births and deaths and assume for a while that migration is insignificant.

3. Population Growth Measures
Percent Rate of Change
(crude birth rate – crude death rate) x 100
Crude Birth Rate = Annual Births/Midyear Population
Crude Death Rate = Annual Deaths/Midyear Population
1991 in United States:
crude birth rate was 17/1000/yr = .017/yr
crude death rate was 9/1000/yr = .009/yr
( ) x100 = .8%/yr

4. Population Growth Measures
Percent Rate of Change
Range in U.S. has been .8% - 1.0% per year
With population of about 300, million this means growth of 2.4 to 3.0 million each year
excluding immigration.

5. Population Growth Measures
Percent Rate of Change
(crude birth rate – crude death rate) x 100
Total Fertility Rate (TFR)
The number of offspring born to the average woman during her lifetime.
TFR is sum of age specific fertility rates (ASFR)
ASFRx = Annual births to women age x /
Midyear female population age x

6. Age Specific Fertility Rates
Births
2000 Women
ASFR
15-19
453,725
9,668,183
.0469
20-24
1,021,627
9,162,263
.1115
25-29
1,058,265
8,855,417
.1195
30-34
942,697
9,889,775
.0953
35-39
451,723
11,087,196
.0407
40-44
92,813
11,473,332
.0080
45-49
5,083
10,202,481
.0005
15-49
4,025,933
70,338,647
.0572
General Fertility Rate

7. Total Fertility Rate Ages ASFR 5 yr Total Cum Sum 15-19 .0469 .2345
20-24
.1115
.5575
.7920
25-29
.1195
.5975
1.3895
30-34
.0953
.4765
1.8660
35-39
.0407
.2035
2.0695
40-44
.0080
.0400
2.1095
45-49
.0005
.0025
2.1120
TFR(2000) =

8. U.S. Total Fertility Rate 1810 - 1997
Source:ECONOMIC REPORT OF THE PRESIDENT 1997, University of St. Louis Missouri

9. Population Age Distribution
U.S. Census Bureau - Population Pyramids
Population Age Distribution
The age distribution of a population reflects past fertility and survival patterns.
Population pyramids are snapshots of population age distributions.
Cambodia

10. Population Age Distribution

11. Population Age Distribution
South Africa

12. Population Growth Measures
Percent Rate of Change
(crude birth rate – crude death rate) x 100
Total Fertility Rate (TFR)
The number of offspring born to the average woman during her lifetime.
Net Reproductive Rate (Ro)
The number of female offspring born to the average woman during her lifetime that live to reproduce.
R0 = f(ASFR, ASDR)