Name the 15 most and 15 least religiously diverse countries
Using information from a now-defunct Wikipedia page
By mean average deviation - that is, by measuring how different the sizes of religious groups are from the average (bigger means less equal populations)
Using major religious categorizations like "Christianity," "Islam," and "Buddhism," not denominations, and including "irreligion"
Data for one of these countries is dubious, and it's not the Vatican... hint hint