Models & Theories
Master Guide
Recognize, define, apply, and critique the 30 highest-frequency models — with real examples and limitations.
The 30 High-Frequency Models
Master Checklist| # | Model / Theory | Core Idea | What AP Questions Ask |
|---|---|---|---|
| 1 | Central Place Theory (Christaller) | How settlements space out to provide goods/services | Identify hexagon market areas, range/threshold, predict higher-order service location |
| 2 | Rank-Size Rule | City sizes follow a predictable rank pattern | Compute/compare expected sizes; spot deviations |
| 3 | Primate City Rule | One city dominates (often >2× the #2 city) | Explain colonial legacy, primacy effects on migration and investment |
| 4 | Concentric Zone Model (Burgess) | US industrial city land use in rings | Label rings; connect to invasion/succession, filtering, disamenities |
| 5 | Sector Model (Hoyt) | Land use in wedges/sectors along transport routes | Explain why high-rent sector extends along corridors |
| 6 | Multiple Nuclei Model (Harris–Ullman) | Cities develop multiple centers (nodes) | Match land uses to nodes (airport, university, port) |
| 7 | Latin American City Model (Griffin–Ford) | Elite spine; CBD + peripheral squatter areas | Identify spine/elite sector, in situ accretion, periferico |
| 8 | Southeast Asian City Model (McGee) | Mix of colonial CBD + port zone + ethnic zones | Identify commercial spine, old port, mixed land use |
| 9 | Bid-Rent Theory (Alonso) | Land value/rent declines with distance from center | Explain competition for accessible land (retail vs housing) |
| 10 | Demographic Transition Model (DTM) | How birth/death rates change with development | Place a country in a stage, predict growth, explain causes |
| 11 | Epidemiological Transition Model (ETM) | Causes of death shift with development | Match stages to disease patterns; discuss disease diffusion |
| 12 | Malthusian Theory | Population grows faster than food → checks | Apply to famine/poverty debates; critique with tech/trade |
| 13 | Boserup Thesis | Population pressure drives agricultural intensification | Explain innovations (terracing, irrigation) as a response |
| 14 | Population Pyramid + Dependency Ratio | Age/sex structure and economic burden | Interpret momentum, aging, youth bulge; compute dependency |
| 15 | Push–Pull Migration Model (Lee) | Migration driven by pushes/pulls + obstacles | Categorize factors; include intervening obstacles |
| 16 | Ravenstein's Laws of Migration | Common migration patterns (short moves, step, urban pull) | Use "laws" to justify observed flows |
| 17 | Zelinsky Mobility Transition Model | Migration patterns change by development stage | Predict rural→urban vs international migration trends |
| 18 | Gravity Model | Interaction increases with size, decreases with distance | Calculate relative interaction; compare city pairs |
| 19 | Distance Decay / Friction of Distance | Effects weaken with distance or cost/time | Explain trade, diffusion, commuting, service areas |
| 20 | Environmental Determinism vs Possibilism | Environment controls vs humans adapt/modify | Critique deterministic claims; show cultural/tech mediation |
| 21 | Sequent Occupance | Places have layers of cultural landscape over time | Explain mixed toponyms, land use layers, architecture |
| 22 | Hägerstrand Innovation Diffusion (S-curve) | Diffusion: slow → rapid → leveling | Sketch/interpret adoption curve; connect to networks |
| 23 | Language Diffusion Models (Tree vs Wave) | Tree = divergence; Wave = spread via contact | Choose model that fits (isolation vs contact) |
| 24 | Geopolitical Theories: Heartland vs Rimland | Who controls "pivot" land or coastal rim controls power | Apply historically and critique modern relevance |
| 25 | Shatterbelt Theory | Conflict-prone region between stronger powers | Identify examples; explain external pressure + internal division |
| 26 | von Thünen Model | Agricultural land use rings around a market | Predict crop placement by transport cost/perishability |
| 27 | Weber Least-Cost Theory | Industry locates to minimize transport + labor costs | Choose site near inputs/market; note agglomeration |
| 28 | Rostow Stages of Economic Growth | Linear development: traditional → mass consumption | Place countries; critique Eurocentric/linear assumptions |
| 29 | Wallerstein World-Systems Theory | Core exploits periphery; semiperiphery mediates | Classify countries; explain dependency/unequal exchange |
| 30 | Clark–Fisher Sector Model | Economy shifts: primary → secondary → tertiary | Link to development, jobs, urbanization patterns |
Step-by-Step Workflow
Any MCQ or FRQIdentify the Theme
- Urban land use → Burgess / Hoyt / MNM / Bid-rent
- Population → DTM / ETM / Pyramids
- Migration → Push-Pull / Ravenstein / Zelinsky
- Development → Rostow / Wallerstein / Weber / von Thünen
Name + Define
Define the model in one sentence. Example: "The DTM explains how birth/death rates shift as a country industrializes."
Apply to the Prompt
Use 2 concrete real indicators — TFR, CBR/CDR, informal settlements, corridors, coal/iron, labor cost, etc.
State a Limitation ⚡
Points hide here. Common assumptions: isotropic plain, closed economy, stable politics, no colonial legacy, universal linear path.
Key Formulas
Compute TheseUrban Models — Must-Know Labels
Sketch TheseRings (Inside → Out)
"Pie Slices"
High-rent and industry form wedges along rail, roads, and water. Sectors radiate out from the CBD.
"Many Downtowns"
Separate nodes like airports, universities, and ports each create their own center and surrounding land uses.
Elite Spine + Periphery
Colonial + Port Mix
Colonial CBD + old port/city, with a commercial spine and strong ethnic quarters. Mixed land uses throughout.
Competing for Access
Different users bid for land. Retail bids highest near the center. Value declines with distance from CBD.
DTM — Stage Clues
High-YieldHigh / High
High CBR, high CDR. Little to no net growth.
CDR Drops Fast
Sanitation/medicine causes CDR to plummet → population boom.
CBR Starts Falling
Urbanization, contraception, and women's education cause CBR to drop.
Low / Low
Both CBR and CDR are low. Stable or very slow growth.
Natural Decrease
CBR falls below CDR. Aging population, population shrinks.
ETM — Stage Clues
Disease PatternsPestilence & Famine
Infectious disease and famine dominate mortality.
Receding Pandemics
Improved medicine and sanitation reduce infectious disease deaths.
Degenerative Disease
Heart disease, cancer, and chronic illness become dominant causes of death.
Delayed + Re-emerging
Delayed degenerative diseases plus re-emerging infections (e.g., antibiotic resistance).
Mini Worked Examples
Apply + Limit Fastvon Thünen — Agricultural Rings
A city market encourages dairy and market gardening close in because they're perishable and costly to ship. Grains and ranching move further out.
Refrigeration, highways, and global trade break the neat ring pattern. Modern supply chains mean dairy can ship thousands of miles.
Demographic Transition Model (DTM)
Country X has a high CBR and rapidly falling CDR due to improved sanitation → Stage 2 rapid population growth.
War, HIV/AIDS, or state policies can interrupt or distort the expected progression through stages.
Central Place Theory (Christaller)
A specialty hospital locates in a regional city because it needs a larger threshold population and people will travel farther (greater range) for specialized care.
Physical barriers, online services, and uneven wealth distort the neat hexagonal spacing the model assumes.
Gravity Model
City A: pop. 2,000,000 | City B: pop. 500,000 | Distance: 100 km
Because distance is squared, doubling the distance cuts interaction to one quarter. If populations are similar, distance decides; if distance is similar, population decides.
Weber Least-Cost Theory
A steel mill needs bulky inputs (iron ore + coal) and sells to a major metro market.
If inputs lose weight during processing, the plant locates near raw material sources to cut bulk transport costs.
Modern firms may prioritize skilled labor, just-in-time logistics, or tax incentives. Agglomeration economies can override transport logic.
Latin American City Model (Griffin–Ford)
Elite high-rise development along one corridor from the CBD = commercial spine/elite sector. Large informal settlements on the periphery match the periferico zone.
Rapid globalization can produce edge cities and polycentric patterns not captured by the model's single-spine structure.
Common Mistakes & Traps
Don't Lose Points HereDTM Stage Mix-Ups
Calling a country "Stage 3" just because it's growing. Stage 3 is defined by a falling CBR, not just population growth.
Look for why CBR is dropping — contraception, women's education, and urbanization are the key indicators.
Treating Models as Universal Laws
Force-fitting Burgess or von Thünen to every city. Models assume flat land, single center, no planning, older industrial context.
Always add a limitation — topography, zoning, highways, globalization, or colonial history all distort model predictions.
Confusing Rank-Size with Primate
Rank-size is a distribution pattern across many cities; primate is one-city dominance. They are not the same thing.
Rank-size: use Pₙ = P₁/n. Primate: check if the largest city is >2× the size of the #2 city.
Diffusion Type Confusion
Describing "spread through social media influencers" as contagious diffusion.
Influencer → others = hierarchical. Neighborhood to neighborhood = contagious. Remember: C-H-S-R (Contagious, Hierarchical, Stimulus, Relocation).
Misreading Population Pyramids
Seeing a wide base and saying "aging population." A wide base means high youth dependency and a high CBR.
Aging shows as a wide top — a rectangular or top-heavy structure with high old-age dependency.
Weber Without Agglomeration
Only mentioning transport costs misses a major component of Weber's own theory.
Add: "Agglomeration economies can pull firms into clusters even if individual transport costs rise slightly."