Demography Study Notes

Demography Overview

• Study of populations: size and composition including age, sex, race, ethnicity.

• Processes altering populations: birth, death, migration, unions.

• Demography divided into formal (math/stats) and population studies (demographic/non-demographic variables).

Vital Statistics Balancing Equation

• Model: $N(t) = N(0) + B[0,t) - D[0,t) + IM[0,t) - OM[0,t)$

• Definitions:

  • $N$ = Population size

  • $B$ = Births

  • $D$ = Deaths

  • $IM$ = In-migration (immigration)

  • $OM$ = Out-migration (emigration)

Population Structure

• Relative distributions by age/sex varies over time and affects demographic events.

• Age-specific rates crucial for analysis.

• Proportions of age groups: pre-reproductive, reproductive, post-reproductive.

  • Human sex ratio at birth: ~1.05 (105 males/100 females).

Human Demography: Population Change

• Proximate causes: fertility, mortality, migration.

• Distal causes: variations between and within populations (e.g., fertility in China vs. India).

Fertility and Fecundity

• Fertility: number of live births; Fecundity: biological capability to reproduce.

• Infertility ≠ lack of fecundity; infecundity = infertility.

• Total fertility rate = births woman would have if experiencing age-specific birth rates in a year.

Migration

• Influenced by push factors (source conditions) and pull factors (destination conditions).

Mortality

• Crude death rates: number of deaths per 1,000/year.

• Life expectancy at birth as a key summary measure.

• Infant mortality rates significantly influence population structure.

Population Growth

• Disparities between less developed countries (LDCs) vs. more developed countries (MDCs).

• Changes driven by birth rates, death rates, and migration.

Population Structures and Predictions

• Future growth influenced by current age and sex ratios; population momentum evident in younger populations.

• Visualization through population pyramids aids understanding of structure and growth.