Modifiable Areal Unit Problem

The modifiable areal unit problem (MAUP) is the finding that statistical results computed on spatially aggregated data depend on the arbitrary choice of how space is divided into zones. Stan Openshaw's 1984 monograph crystallized the issue into two intertwined components — a scale effect, where results change as data are grouped into larger or smaller units, and a zoning effect, where results change when the boundaries are redrawn at a fixed scale. Because the units used in geography (census tracts, districts, grid cells) are almost always modifiable rather than natural, almost every aggregate spatial statistic is potentially an artefact of its zonation.