AP Human Geography — Cheatsheet
Formulas, exam-day tips, and key terms on one page.
Formulas & relationships
Reading map scale
large-scale map = small area, more detail | small-scale map = large area, less detail
The scale ratio (1:1,000 vs 1:1,000,000) works like a fraction: 1/1,000 is larger than 1/1,000,000, so 1:1,000 is the “large-scale” map even though it covers less ground.
Three measures of population density
arithmetic = people / total area | physiological = people / arable land | agricultural = farmers / arable land
A high physiological density with a low agricultural density (developed) vs. a high agricultural density (developing) tells you about pressure on farmland and the level of agricultural technology.
Natural increase & doubling time
NIR (%) = (CBR − CDR) / 10 doubling time ≈ 70 / NIR(%)
Crude birth/death rates are per 1,000 people, so dividing their difference by 10 converts to a percent. The Rule of 70 then estimates years to double. NIR ignores migration.
Von Thünen’s core relationship (bid rent)
land rent a farmer can pay ↓ as distance to market ↑, offset by lower transport cost for durable goods
Perishable, heavy, low-value-per-weight goods (milk, vegetables) locate near the market; durable, light, high-value goods (grain, livestock) locate farther out. Each land use outbids the others in the ring where it is most profitable.
On the exam
- On the exam, never call a projection “wrong.” Frame every map choice as a **trade-off**: name the property preserved (shape, area, distance, or direction) and the property sacrificed, then tie it to the map’s purpose. That reasoning earns the point.
- When a prompt gives arable land, expect **physiological** or **agricultural** density, not arithmetic. Label your units (“people per km² of arable land”) and interpret the number — high physiological density = pressure on farmland; low agricultural density = developed, mechanized farming.
- On the exam, first decide **relocation vs. expansion**: did people *move* and carry the trait (relocation), or did it spread while staying strong at the source (expansion)? Only then choose the expansion sub-type — contagious, hierarchical, or stimulus.
- Keep the vocabulary exact: **state = country** (sovereign political unit), **nation = a people** (shared identity). A **nation-state** matches them; a **stateless nation** is a people with no country; a **multinational state** is one country with many nations. Sloppy use of these words costs FRQ points.
- Von Thünen’s rings turn on two variables: **perishability** and **transport cost** (relative to product value and weight). Innermost ring = perishable/heavy/low-value-per-weight; outermost = durable/light/high-value-per-weight. Cite these, not climate or soil, since the model assumes uniform physical conditions.
- Keep the three North American models distinct by their shape: **Burgess = rings** (concentric zones), **Hoyt = wedges** (sectors along transport lines), **Harris–Ullman = multiple nodes** (no single center). One word each — rings, wedges, nodes — anchors the answer.
- Weber in one rule: **bulk-reducing → locate near raw materials** (inputs are heavy); **bulk-gaining or perishable → locate near the market** (the product is heavy or spoils). Identify which weighs more — inputs or output — and the location answers itself.
How to get a 5
- Vocabulary is paramount in APHG. Do not just memorize definitions; be able to apply them to real-world examples (e.g., identify an actual primate city, not just the definition).
- Always consider scale. A phenomenon might look different at the local, national, and global scales. The exam frequently asks how scale changes an analysis.
- When discussing models (Von Thünen, DTM, Central Place), know the assumptions they are based on and the reasons why they might not perfectly fit the modern world.
- In FRQs, pay close attention to the verb. 'Identify' requires only a short answer. 'Describe' requires traits/characteristics. 'Explain' requires cause and effect (the 'how' or 'why').
Key terms
Demographic Transition Model (DTM) — Stages 1-5 showing population change over time. High birth/death rates (1) transition to low birth/death rates (4) as a country industrializes.
Thomas Malthus' Theory — Predicted population grows exponentially while food production grows linearly, leading to mass starvation. (Mostly avoided due to the Green Revolution).
Relocation vs. Expansion Diffusion — Relocation: trait moves with migrating people (e.g., Spanish in Latin America). Expansion: trait spreads outward from a hearth (includes hierarchical, contagious, stimulus).
Von Thünen Model — Agricultural model. Rings outward from market: 1) Dairy/Market Gardening (perishable/expensive transport), 2) Forest, 3) Extensive Crops (wheat), 4) Ranching (livestock).
Green Revolution — Mid-20th century. Introduction of high-yield seeds (wheat/rice), chemical fertilizers, and pesticides. Massively increased food production but caused environmental damage.
Centripetal vs. Centrifugal Forces — Centripetal forces UNIFY a state (e.g., shared language, nationalism). Centrifugal forces DIVIDE a state (e.g., ethnic conflict, geographic barriers).
Gerrymandering — Redrawing political voting districts to favor one political party. Types include 'packing' (concentrating opposition) and 'cracking' (diluting opposition).
Christaller's Central Place Theory — Explains the spatial distribution of human settlements using hexagons. Larger settlements are fewer and farther apart, providing higher-order goods/services.
Concentric Zone vs. Sector Model — Burgess Concentric: city grows in rings outward from CBD. Hoyt Sector: city grows in wedges/corridors following transportation routes.
Rank-Size Rule vs. Primate City — Rank-size: nth largest city is 1/n the size of the largest. Primate city: the largest city is more than twice as large as the second and dominates politically/economically (e.g., Paris, Mexico City).
Rostow's Stages of Economic Growth — Modernization model (5 stages): Traditional society → Pre-conditions for take-off → Take-off (industrialization) → Drive to maturity → High mass consumption.
Core-Periphery Model (Wallerstein) — World Systems Theory. Core countries (rich/industrialized) exploit Periphery countries (poor/raw materials). Semi-periphery are developing (e.g., BRICS).