Foundational Concepts & Measures

1. Foundational Concepts & Measures Monday, Sept 13

2. The Balancing Equation of Population Change Ending Population Starting Population Births Deaths Moves In Moves Out Natural Increase Net Migration

3. Ratios • A single number expressing the relative size of two other numbers X/Y = ratio of X to Y • Examples • Dependency ratio • Sex ratio • Population density • Child-woman ratio • Unemployment rate

4. Proportions • Special type of ratio where the denominator includes the numerator • Example: Proportion of deaths that occurred to males Dm ------------------- Dm + Df

5. Demographic Rates Number of Occurrences ------------------------------- Person-Years of Exposure to the Risk of Occurrence Rate =

6. Person-Years • Method of calculating exposure to risks • How to obtain • Count them (life lines) • Estimate by counting people alive at various points and weighting each count by the proportion of the year • Use mid-year population

7. Principle Period Rates • Crude Birth Rate (CBR) • Crude Death Rate (CDR) • Crude Rate of In-migration (CRIM) • Crude Rate of Out-migration (CROM) • Crude Rate of Natural Increase (CRNI) • Crude Rate of Net Migration (CRNM)

8. Growth Rates • Crude Growth Rate • Linear Change • Instantaneous Change • With a constant rate of change (r*) • Mean annualized growth rate (¯r) • Doubling Time

9. Cohort • Aggregate of units that experience a particular event during a specific time interval • Limitations of cohort studies • Losing track of individuals/loss to follow-up • By the time all info is collected, it is ancient

10. Probabilities • The denominator is composed of all those persons in the given population at the beginning of the period of observation

11. Age of a Population • What has more influence on the age of a population? Births or deaths? Why? • Why do falling death rates make a younger population? • Population pyramids