With his prediction of the collapse of the Evangelical church, however, he seems off the mark. Because the semester just ended, I have some time to go into depth on this issue. Having said that, articles like that of by Mr. Spencer attract a lot of attention quickly, so my writing about it two months after publication is an eternity in the blogosphere. Nonetheless, here goes.
Spencer's prediction is that "We are on the verge – within 10 years – of a major collapse of evangelical Christianity. This breakdown will follow the deterioration of the mainline Protestant world and it will fundamentally alter the religious and cultural environment in the West."
Well, predictions can be difficult, so let's look at the recent past.
As you can see, the percentage of Evangelicals in the country has increased since 1970, the percentage Mainline Protestants has dropped considerable, and the percentage Catholics has remained about the same.
Now, there are a lot of things would could say (and have been said) about these data, but at just a glance, it's pretty clear that there's no evidence of the percentage of Evangelicals dropping precipitously--and the data go right up to 2008.
This has two implications.
1) Since these data give the percentage of American adults who attend an evangelical church, and the American population has been growing, that means the actual number of American Evangelicals has increased substantially in the past 35 years.
2) Given no evidence of a collapse, Mr. Spencer would seem to have the burden of explaining why this sudden change will happen.
For me, this finishes the discussion. Unless there's some sort of magic ball involved that can predict things that have yet started happening, the discussion is over.
Technical stuff: The data come from the General Social Survey using the Reltrad classification scheme which identifies evangelicals as people who go to evangelical churches (as opposed to people who describe themselves with that label). I smoothed out the lines using loess smoothing in STATA.