CHAPTER SIX
Demographic Methods for the Sociology of Religion
Michael Hout
The sociology of religion may not overlap with demography in many people’s minds,
but two facts about the past one hundred years of American religion indicate how de-
mography helps shape the religious landscape. Fact 1: Most people practice the religion
their parents taught them. That means that the principal factor in the changing reli-
gious composition of any given society (and of the United States in particular) is the
number of children each adult has to teach, that is, the relative fertility rates of different
religions (Hout, Greeley, and Wilde 2001). Fact 2: Most people who have switched from
one religion to another have switched from their parents’ religion to their spouse’s re-
ligion. That means that the prevalence, timing, and selectivity of marriage also affects
the distribution of people across religions. In this chapter, I will lay out some of the
demographer’s concepts and methods that have the greatest utility for the sociologist
of religion.
To motivate attending to the details, however, let us consider a “thought exper-
iment” – not a flight of fancy, something close to the way societies are organized.
Imagine a country that has two religions, one larger than the other. Imagine further
that, over time, the minority religion grows faster than the majority one. To be realis-
tic, it would be okay to imagine that the population as a whole grows and that both
groups grow with it; the key condition is that the smaller one is growing faster than
the larger one. Throw in one more (realistic) supposition: Suppose that in the imagined
country most people practice their parents’ religion at a rate comparable to the rate
at which Americans do. If these three things are all true, then, as time goes on, the
minority religion will come closer and closer to being the same size as the larger one.
Given enough time and a constant difference in fertility, the minority religion would
eventually become as large as the majority religion; they could even reverse rank, that
is, the one that was originally smaller could become the majority religion and the one
that was originally larger could become the minority religion.
Casual observers of the imagined society I was referring to would wonder why the
minority faith was growing. Some might figure that members of the initially larger
religion were switching to the smaller alternative. But we know it’s demography, not
switching that is changing the population. In fact, the country’s religious distribution is
changing without any individual actually changing religion. The combination of differ-
ing demography and stable intergenerational religious socialization would be sufficient
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