In
demographics
Demography () is the statistical study of populations, especially human beings.
Demographic analysis examines and measures the dimensions and dynamics of populations; it can cover whole societies or groups defined by criteria such as edu ...
, the rank mobility index (RMI) is a measure of a
city
A city is a human settlement of notable size.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. London: Routledge. It can be def ...
's change in
population rank
Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction using a ...
among a group of cities.
Formally
:
where
* ''R''
1 = city's rank at time 1
* ''R''
2 = city's rank at time 2
A RMI value must be between −1 and 1. A RMI of 0 indicates no change.
Index numbers