1️⃣ Demographic Transition Model (DTM)
Mnemonic: High → Drop → Drop → Low → Decline
- Stage 1: High births & deaths → tiny growth 🏹⚰️
- Stage 2: High births, deaths drop → boom 💉🏥
- Stage 3: Births drop → moderate growth 🏭
- Stage 4: Low births & deaths → stable 🏙️
- Stage 5: Very low births → decline 👵👴
Tip: Stage 2 = "explosion", Stage 5 = "shrinking old people"
2️⃣ Epidemiologic Transition Model (ETM)
- Stage 1: Famine & disease 🍖🦠
- Stage 2: Receding pandemics 🚰🧼
- Stage 3: Degenerative/chronic diseases 🫀🦴
- Stage 4: Delayed degenerative ⏳❤️
- Stage 5: Reemerging diseases 😷💉
3️⃣ Population Math & Density
- CBR: births per 1000
- CDR: deaths per 1000
- NIR: (CBR – CDR) ÷ 10
- TFR: total kids per woman (replacement = 2.1)
- Doubling time: 70 ÷ NIR
Densities
- Arithmetic: total people / total land 🏠
- Physiological: people / farmable land 🌾
- Agricultural: farmers / farmable land 👩🌾
4️⃣ Population Growth Patterns
- Fastest growth: Sub-Saharan Africa 🌍🔥
- Declining population: Europe, Japan ⬇️❄️
- Dependency ratio: too many young & old 🧒👵
5️⃣ Migration Basics
Ravenstein’s Laws
- Most move short distances 🚶♂️
- Long-distance → big cities 🌆
- Each flow has a counterflow 🔄
- Mostly rural → urban 🌾➡️🏙️
- Young males move first 👦
Zelinsky Migration Transition
- Stage 2 → emigration 🏃♂️
- Stage 3–4 → immigration 🛬
Gravity Model
- Big + close = strongest migration 💥
6️⃣ Population Theories
- Malthus: Population grows exponentially, food grows arithmetically → famine ⚠️
- Neo-Malthusian: adds resources & climate 🌎🔥
- Critics: technology can prevent famine ⚙️🌾
7️⃣ Population Policies
- Pro-natalist: encourage babies 👶✨
- Anti-natalist: limit babies ✋👶
- Eugenic: favor 1 group 🧬❌
8️⃣ Push & Pull Factors
- Push: war, famine, no jobs 💣🌾
- Pull: safety, jobs, education 🏡💼
- Voluntary: choice ✈️
- Forced: war/slavery ⚔️
- Environmental: climate 🌊🌪️
⚡ Memory Hooks
- “Sanitation Saves” = Stage 2 ETM
- “Education Ends Baby Booms” = Stage 3–4 DTM
- “Africa Accelerates” = fastest growth
- “Big + Close → Gravity Flow”
- “Malthus = Math Problem (Pop > Food)”