Alternative Formulas for Selected Indices

Abstract

The values of all popular indices of uneven distribution can be obtained using a variety of mathematically equivalent computing formulas. For a given index some formulas are more familiar and widely used than others, but no single formula can be declared sacred or best for all purposes. The many alternatives can be confusing to those who are new to segregation research. But their availability benefits researchers by providing a variety of options from which to choose to best serve the needs of a particular study. The relevant considerations can include factors such as efficiency of computation, ease of explaining the index to broad audiences, relevance for establishing appealing substantive interpretations, capacity for enabling practical tasks such as decomposition analysis or the calculation of spatial versions of index scores, and utility for pinpointing technical issues in segregation measurement. Researchers may choose a particular formula specifically to serve the needs of a given study. Or they may use a formula based on familiarity and habit. But in one crucial sense the choice is unimportant as all valid formulas can be used interchangeably without affecting the results of individual index scores, research findings, and substantive conclusions.