Modifiable Areal Unit Problem (MAUP)
MAUP
A source of statistical bias where point-based measures of spatial phenomena are aggregated into districts, (such as population density or illness rates), and the resulting summary values (e.g., totals, rates, proportions, densities) are arbitrarily influenced by both the shape and scale of the aggregation unit.
Origin
The issue was first recognized by Gehlke and Biehl in 1934, though the term "MAUP" was coined by Stan Openshaw and Peter Taylor in 1979. Openshaw formalized the concept in his influential 1984 CATMOG publication, observing that "the areal units used in many geographical studies are arbitrary, modifiable, and subject to the whims of whoever is doing the aggregating." Geographer Michael Goodchild later suggested calling it the "Openshaw effect."