It’s fairly common to hear the claim that religious belief in America has been very stable over the years. That’s true to some extent, but a look at Gallup’s long-term trend data suggests that the long-term stability may be changing, and that change corresponds nicely with the Bush era or perhaps the “war on terror.”
The plot below shows data from a question Gallup has asked regularly for decades: “How important would you say religion is in your own life: very important, fairly important, or not very important?”
The place of religion was indeed very stable for decades, at least at the resolution Gallup was sampling. Somewhere between 2001 and 2003, the number of people who found religion “not very important” started rising (as shown by the locally weighted regression, aka “loess” regression), and is now above the level it ever hit in the preceding decades. The number finding religion “very” and “fairly” important is much noisier, but it appears that “fairly” is holding steady, while fewer are finding it “very” important.
The upward trend among the religiously apathetic and the decline in strong religious believers both seem to be resistant to small changes in the data. The softer coloration represents a series of loess regressions based on repeated resamplings (with replacement) of the original data, an approach which helps show the range of variation intrinsic to the data. A straight line could pass through the blue cloud, so there seems to be no change in those numbers, at least none that apparent in the data thus far.
It’s noteworthy that the shift away from strong belief and toward indifference precedes the recent spate of atheist books, and falls somewhere between the 9/11 attacks and the invasion of Iraq. Whether those demonstrations of the dangers of religious extremism drove people towards a greater skepticism towards religion is hard to say, but is certainly at least plausible. The trend also follows the defeat of the first round of creationist science standards in Kansas, and corresponds to a shift in attitude on issues from gay marriage to stem cells. It will be interesting to continue following this trend, and see whether it persists.