Religious group size, demographic composition, and the dynamics thereof
are of interest in many areas of social science including migration, social
cohesion, parties and voting, and violent conflict. Existing estimates however
are of varying and perhaps poor quality because many countries do not
collect official data on religious identity. We propose a method for accurately
measuring religious group demographics using existing survey data:
Bayesian multilevel regression models with poststratification. We illustrate
this method by estimating the demography of Muslims, Hindus, and Jews in
Great Britain over a 20-year period and validate it by comparing our
estimates to UK census data on religious demography. Our estimates are
very accurate, differing from true population proportions by as little as 0.29
(Muslim) to 0.04 (Jewish) percentage points. These findings have implications
for the measurement of religious demography as well as small group
attributes more generally.
