Economics has special ways of dealing with time-series theses like "The Christian Right got into politics, and their share of the population went down. Therefore, it must have been because of the politics." On its own, this has little empirical content: post hoc ergo propter hoc. But a good analysis can be convincing by showing parallel data. We can examine other religions that didn't get into politics (or didn't change their relative immersion into politics), or look at factions of Christianity that went into politics more.
In other words, we can say "if that thesis is true, then it has testable implications." Corrections offers two testable implications:
- Other branches of Christianity haven't gone into politics as much as Evangelicals: therefore, Evangelicals should be suffering the most.
- Judaism, a religion strongly tied to the left for more than a century, has not changed its political position very much. Therefore, it should be untouched by the last twenty years.
click to enlarge):
This figure tells our whole story: if being political has hurt Christians, then why has Judaism, which hasn't changed its political orientation seen a larger fall, while the subset of Evangelicals in Christianity seen the largest rise?
As a note, it is true one can begin to tell stories (ex: Evangelicals rose by draining other Christians while the rest left, Judaism has its own thing going on, etc.) to make sure Merritt's claim is devoid of testable hypotheses. Such a tack would ironically and safely bring one's own politics into a religious (non-testable) sphere.