Measuring the effect of "ethnicity"

Most tests of hypotheses about the effects of "ethnicity" on outcomes use data or measures that confuse or conflate what are termed ethnic structure and ethnic practice. This article presents a conceptualization of ethnicity that makes the distinction between these concepts clear; it demonstrates how confusion between structure and practice hampers the ability to test theories; and it presents two new measures of ethnic practice-ECI (the ethnic concentration index) and EVOTE (the percentage of the vote obtained by ethnic parties)-that illustrate the pay-offs of making this distinction and collecting data accordingly, using examples from the civil war literature.