able. At any point another “Great Awaken-
ing” could reverse these trends. But among
social changes, demographic predictions
are relatively safe; the events they predict
have, in some sense, already happened.
The people who will turn 40 years old in
2037 are turning 20 this year, and we al-
ready have data about them. The people
who will turn 20 in 2037 have been or soon
will be born. So these predictions will only
be wrong if current teenagers are more re-
ligious than people in their 20s, or if cur-
rent children are being raised in a more re-
ligious environment. But in both cases, the
opposite is more likely to be true.
In fact, there are reasons to think these
predictions are conservative: 1. Survey re-
sults like these are subject to social desir-
ability bias, which is the tendency of re-
spondents to shade their answers in the
direction they think is more socially ac-
ceptable. To the degree that apostasy is
stigmatized, we expect these reports to
underestimate the number of Nones. As
the visibility of nonreligious people in-
creases, they might be more willing to be
counted; in that case, the trends would go
faster than predicted.
- The trends for Protestants and Nones
have apparent points of inflection near - Predictions that include earlier data
are likely to underestimate future trends. If
we use only data since 1990 to generate
predictions, we expect the fraction of Nones
to exceed 40 percent within 20 years.
A longer version of this article is avail-
able from my blog, “Probably Overthink-
ing It.” It applies the same methods to pre-
dict changes in other aspects of religion:
belief in God, interpretation of the Bible,
and confidence in the people who run reli-
gious organizations.
The data I used and all of my code are
available in this Jupyter notebook.
—Allen Downey
facebook.com/ScientificAmerican
Like us on Facebook