What does the Rank-Size Rule describe about city distributions in urban systems?

• A. The nth largest city is roughly 1/n the size of the largest; indicates primacy if one city dominates
• B. The sum of city sizes equals the square of the largest city
• C. Population sizes are equal across all cities
• D. City sizes are random with no pattern

Answer: (A)

The idea being tested is how city sizes tend to distribute in an urban system: as you rank cities from largest to smallest, each city's population tends to be roughly inversely related to its rank. This means the largest city sets a reference, the second-largest is about half as large, the third about a third, and so on. This pattern is the Rank-Size Rule, often described as Zipf’s law in geography. It helps explain primacy because when one city greatly dominates in size, the sequence shows a strong disparity between the top city and the rest. Saying that the nth largest city is roughly 1/n the size of the largest captures that inverse relationship and the potential for a dominant city. The other options don’t fit this pattern: equal sizes imply no rank-based distribution, summing to the square of the largest isn’t how city sizes scale, and randomness would show no consistent pattern.