By Guest Contributor Philip N. Cohen, PhD; originally published at Sociological Images
Trying to summarize a few historical trends for the last half century, I thought of framing them in terms of diversity.
Diversity is often an unsatisfying concept, used to describe hierarchical inequality as mere difference. But inequality is a form of diversity–a kind of difference. And further, not all social diversity is inequality. When people belong to categories and the categories are not ranked hierarchically (or you’re not interested in the ranking for whatever reason), the concept of diversity is useful.
There are various ways of constructing a diversity index, but I use the one sometimes called the Blau index, which is easy to calculate and has a nice interpretation: the probability that two randomly selected individuals are from different groups.
Take religion. According to the 2001 census of India, this was the religious breakdown of the population:
Diversity is calculated by summing the squares of the proportions in each category, and subtracting the sum from 1. So in India in 2001, if you picked two people at random, you had a 1/3 chance of getting people with different religions (as measured by the census).
Is .33 a lot of religious diversity? Not really, it turns out. I was surprised to read on the cover of this book by a Harvard professor that the United States is “the world’s most religiously diverse nation.” When I flipped through the book, though, I was disappointed to see it doesn’t actually talk much about other countries, and does not seem to offer the systematic comparison necessary to make such a claim.
With our diversity index, it’s not hard to compare religious diversity across 52 countries using data from World Values Survey, with this result:
The U.S. is quite diverse–.66–but a number of countries rank higher.