Chapter 4: Canada's Population in a Global Context

Introduction

All 3 key demographic processes are dependent on age
All 3 key demographic processes are related to sex and gender
- Survival advantage of women over men
Composition: the distribution of the population in accordance with the intersecting characteristics of age and sex

Age distribution: those under 15 (youth), those aged 15-64 (working age), and those aged 65+ (post-retirement)
- These are approximations
- To get a sense of the economic dependency burden in a given society
Total dependency ratio: the ratio of youth + old-age dependents ÷ working-age population
- Obtain a measure of a society’s overall dependency on the workers, who must provide for those not in the labor force
Dependency ratio:
- If it is greater than 100 → more dependents than workers in the population
- If it is below 100 → more workers than dependents in the population
Populations with relatively large old-age components tend to have relatively small youth components and have a relatively high median age

Age-sex pyramid: a pictorial representation of the age and sex composition of the population
Median age: the age that divides the distribution in half (half the population is above the median and the other half is below)

Demographic transition
- Early stages: age pyramid = pagoda-like (wide base and narrowing structure)
- Most explosive growth stage: triangular shape
- Post-transitional phase: urn-shaped pyramid (narrow bottom, large bulge in the middle, sharp narrowing at the top)
Aging transition: societies pass from an initially young to an eventual aging structure
Canada: urn-shaped pyramid
- Bulge in middle, largest segment of population → baby boom generation
Stable population: structure with very low constant rates of natural growth
Stationary age structure: structure in which annual rates of natural increase remain exactly zero indefinitely due to equal numbers of births and deaths annually

Shifts in age composition are caused by changes in fertility (mostly) and mortality
Intrinsic rate of natural increase: the difference between the intrinsic birth rate and the intrinsic death rate
- Intrinsic birth rate: rate at which mothers bear their daughters in a stable population, determined by a set of constant age-specific birth rates
- Intrinsic death rate: death rate in a stable population, determined by a set of constant age-specific death rates

Life expectancy at birth: measure of survival determined by a populations’ age-specific mortality rates
- Higher life expectancy = better survival probability
Gross reproduction rate (GRR): measures the average number of daughters born to a women, given a prevailing schedule of age-specific fertility rates
- Greater GRR = higher fertility
Declining mortality → makes the age distribution younger
- Because more young people + more births
When mortality declines are in infancy/early childhood = younger population
When mortality declines are in the ages 45+ = aging population → advanced societies today

Negligible! In large national populations, any amount of migration will only have a minor impact
Age pyramid of foreign-born population: diamond-shaped (few immigrants below 15 and 65)

2 populations with different age structures will converge to identical age compositions if they have identical age-specific birth and death rates over 70 years or more
- Example: Sri Lanka + Sweden
Ergodic property of populations: the tendency for populations to eventually “forget” their initial age distributions
Time it takes for a population’s age structure to change completely: 100 years

Population momentum: M = the size of the stationary population ÷ size of the initial population
- M is greater than 1: population increase
- M = 1: no momentum
- M is below 1: population decline
Useful for planning purposes
Net reproduction rate (NRR): measure of a population reproductivity. the extent to which mothers replace themselves by bearing daughters, taking into account mortality to women in the reproductive ages

Sex ratio: numerical balance between males and females in a population
- Should be close to 100 males per 100 females
- Primary sex ratio: ratio of males to females at conception
- Secondary sex ratio: ratio of males to females at birth
- Tertiary sex ratio: ratio of males to females at birth beyond infancy

Human sex ratio at conception = 115/130 males for every 100 females
- Cause: males are at greater risk of death than females throughout the entire lifecycle

Secondary sex ratio depends on 2 factors:
- The sex ratio at conception
- Sex-selective loss during pregnancy
Normal range: 103-107 boys born for 100 girls
- More male than female fetuses are lost to spontaneous abortion or stillbirth
Sex-ratio at birth is controlled by parental hormone levels at the time of conception
- Severe stress
- Highly traumatic events
Evolutionary biology theory: in the animal kingdom, pregnant females when faced by severe stressors preferentially abort frail male fetuses
- Not proven in humans

High sex ratio for black and white populations (more men than women): low levels of family disruption, high rates of violent crime
Low sex ratio (more women than men): low rates of violent crime, high levels of family disruption
→ Direct positive effects on the sex ratio on rates of criminal violence and negative indirect effects via family disruption