# Urban Geography and City Systems

History I · Geography · https://tryals.app/learn/history-i/urban-geography-and-city-systems

## Cities Come in Systems

A city is never alone. It sits in a system of cities with a shape regular enough to be startling.

The **rank-size rule** states that in a mature urban system, the nth largest city has about $1/n$ the population of the largest. The formula is $P_n \approx P_1 / n$. This empirical regularity holds across wildly different countries and centuries.

The interesting cases are violations. A **primate city** is far bigger than rank-size predicts, often several times the second city, as seen in Paris, London, or Seoul. This is the signature of a centralized state, imperial capital, or colonial economy funneling exports through one port.

The **missing middle** is the classic colonial pattern of one huge port and tiny villages with no mid-sized cities. It reveals an economy built for extraction rather than an internal market.

## Why Cities Sit Where They Sit

**Central place theory** (Christaller, 1933) explains city spacing using two concepts. **Range** is how far someone will travel for a good, and **threshold** is the minimum population needed to sustain it. Bakeries have small ranges and thresholds; cardiac surgery units have huge ones, creating a hierarchy.

| Model | Claim | Fits | Pitfall |
|---|---|---|---|
| **Concentric zone** | Rings outward from CBD | Industrial Chicago | Breaks in Europe |
| **Sector** | Wedges along transport | Rail/river cities | Generalizes poorly |
| **Multiple nuclei** | Several centres | Car-based cities | Use as vocabulary |

Cities exist because **proximity is productive**, lowering the cost of exchange and imitation. Historically, cities were demographic sinks that grew only by in-migration from the countryside.

## Practice questions

7 of this lesson's 12 practice questions, with answers. The full set is in the app.

### 1. A country’s largest city has 8 million people. Under the rank-size rule, roughly what population would the 4th largest city have?

**Answer:** 2 million (within ±0.3)

**Why:** Two million. The rule is rough and empirical rather than a law, but it holds across strikingly different countries and centuries, which is exactly why the deviations are worth reading.

Page: https://tryals.app/practice/history-i/urban-geography-and-city-systems/a-countrys-largest-city-has-8-million-people-under-the-rank-size

### 2. A country's largest city is eight times the size of its second. What does that departure from the rank-size rule usually indicate?

A. Nothing; the rank-size rule is a statistical curiosity without meaning
B. Concentration of power or extraction in one place
C. That the country is unusually urbanised overall
D. That the second city is in demographic decline

**Answer:** B. Concentration of power or extraction in one place

**Why:** A rank-size distribution grows out of many interacting centres, and primacy signals that one node captures administration, trade or extraction disproportionately, colonial capitals are the classic case. It is a diagnostic rather than a law, which is why the interesting work is explaining the departure.

Page: https://tryals.app/practice/history-i/urban-geography-and-city-systems/a-countrys-largest-city-is-eight-times-the-size-of-its-second-what

### 3. Sort each urban model by its central claim.

**Answer:**

- Rings from the centre: Burgess concentric zone model, Zones expanding outward from the CBD
- Wedges along routes: Hoyt sector model
- Several separate centres: Harris–Ullman multiple nuclei model

**Why:** All three are Chicago-shaped and generalize badly, a European city with a medieval core breaks Burgess on contact. Vocabulary, not laws.

Page: https://tryals.app/practice/history-i/urban-geography-and-city-systems/sort-each-urban-model-by-its-central-claim

### 4. Pre-modern cities had death rates above their birth rates and grew only through migration.

**Answer:** True

**Why:** True. Crowding, contaminated water and epidemic disease meant cities consumed population; London needed a continuous inflow from the countryside merely to hold steady. Urban growth was therefore a rural story, and the pattern only broke with nineteenth-century sanitation.

Page: https://tryals.app/practice/history-i/urban-geography-and-city-systems/pre-modern-cities-had-death-rates-above-their-birth-rates-and-grew

### 5. Why do cities exist at all?

A. Agricultural surpluses had to be stored centrally
B. States mandated urban settlement for taxation
C. Defensive walls required concentrated populations
D. Proximity is productive: it lowers the cost of exchange

**Answer:** D. Proximity is productive: it lowers the cost of exchange

**Why:** Density is the product, not a side effect. It lowers the cost of exchanging, of finding the right person, and of copying what works, which was worth dying young for, and demonstrably was.

Page: https://tryals.app/practice/history-i/urban-geography-and-city-systems/why-do-cities-exist-at-all

### 6. In a rank-size system whose largest city has 12 million people, roughly what population would the 3rd largest have?

**Answer:** 4 million (within ±0.75)

**Why:** Four million, $12/3$. Simple enough to check on any country’s census, which is precisely how you find the ones that do not fit.

Page: https://tryals.app/practice/history-i/urban-geography-and-city-systems/in-a-rank-size-system-whose-largest-city-has-12-million-people

### 7. What can the shape of a city-size distribution tell you?

A. A rank-size fit suggests a mature, internally integrated system
B. A missing middle suggests an economy built to extract to the coast
C. The distribution reveals the average income of each city
D. A primate city suggests a system organized around one centre

**Answer:** A. A rank-size fit suggests a mature, internally integrated system; B. A missing middle suggests an economy built to extract to the coast; D. A primate city suggests a system organized around one centre

**Why:** The distribution is a diagnostic of how an economy is wired. What it cannot tell you is anything about wealth, a huge primate city can be poor, and frequently is.

Page: https://tryals.app/practice/history-i/urban-geography-and-city-systems/what-can-the-shape-of-a-city-size-distribution-tell-you