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	Urban Primacy Index	Central Place Analysis
Field	Human Geography	Human Geography
Family	Process / pipeline	Process / pipeline
Year of origin	1939	1933
Originator	Mark Jefferson	Walter Christaller
Type	Index of the dominance of the largest city in an urban system	Theory and analytic framework for the size, number, and spacing of settlements
Seminal source	Jefferson, M. (1939). The Law of the Primate City. Geographical Review, 29(2), 226–232.	Christaller, W. (1966). Central Places in Southern Germany (C. W. Baskin, Trans.). Prentice-Hall. (Original work published 1933). ISBN: 9780131226302
Aliases	Primacy Index, Primate City Index, Two-City Primacy Index, Four-City Primacy Index	Central Place Theory, Christaller Central Place Model, Settlement Hierarchy Analysis, Central Place Hierarchy
Related	4	4
Summary	The urban primacy index measures how dominant a country's largest city is relative to the cities below it in the size hierarchy. It grows out of Mark Jefferson's 1939 law of the primate city, which observed that many countries are headed by a single city far larger and more important than any other. The simplest two-city index divides the largest city's population by the second-largest's, while the four-city index compares the leading city with the combined size of the next three, giving a compact gauge of urban concentration.	Central place analysis is the study of the size, number, and spacing of settlements as service centres, grounded in Walter Christaller's central place theory of 1933. It explains why settlements form an orderly hierarchy — many small villages, fewer towns, a handful of cities — and why higher-order centres are spaced farther apart and offer more specialized goods, deriving the famous nested pattern of hexagonal market areas from two economic concepts: the range and the threshold of a good.