Population and Migration: Composition, Change, and Movement
Core concepts
Track population through density (arithmetic, physiological, agricultural) and distribution. The demographic transition model (DTM) links birth and death rates across stages: Stage 1 high–high, Stage 2 high birth with falling death (rapid growth), Stage 3 falling birth, Stage 4 low–low, and Stage 5 in some models with births below deaths. Epidemiologic transition and Malthusian versus neo-Malthusian arguments (and critics like Boserup, who saw population pressure driving innovation) are staples. Know population pyramids: wide base = high birth rates and young dependency; narrow base with a bulge = aging or a past baby boom. Dependency ratio and sex ratio appear in data questions. Push and pull factors drive migration; distinguish voluntary from forced migration, internal from international, and circulation (repetitive, short-term) from migration (permanent move). Ravenstein's laws note that most migrants move short distances and that migration is often stepwise. Chain migration, transnationalism, and remittances connect migration to culture and economy.
Traps and a worked example
Do not assume a high total population means high density (compare a crowded small country with a vast sparsely settled one). Do not read a pyramid's wide top as high birth rates-it signals an older population. Remember that Stage 2 growth is driven by falling death rates, not rising births.
Worked example: A country has a broad base tapering sharply-consistent with Stage 2 of the DTM, high natural increase, and a high youth dependency ratio, implying pressure on schools and future labor supply.