Clark of Mormon Metaphysics says below:
My impression is that atheists, Mormons and Jews did best simply because all three groups tend to be well educated. (Someone mentioned stats adjusted for education but I couldn’t see where that was noted although maybe I just missed the obvious)
This is not an unfounded assertion, as it is "common knowledge" in the Zeitgeist that Mormons are high achievers. Ergo, posts such as The Latter Day Ruling Class. There's one problem here: it's not really true in a full-throated sense. The sample size for Mormons in the GSS is very small, so that's not what we need to look at. First, American Religious Identification Survey 2008:
As you can see Mormons have about the average proportion of college graduates for an American ethno-religious group. We can drill-down further with the Religious Landscape Survey. First, comparisons of various religious groups by educational attainment class as proportions:
OK, now let's look at income:
As you can see Mormons rank below Mainline Protestants, and well below Jews. A notable trend though is that Mormons seem to have lower variance than the national sample. There are fewer Mormons at the extremes. Finally, here's how Mormons stack up on IQ using a NLSY sample:
These data data seem to imply that Mormons are average white folk. So why the perception that they're more educated? Part of it probably has to do with the reality that the "floor" of Mormon achievement is above the national norm. Fewer high school dropouts, fewer poor people. But I think another issue is what I'll call "The Mitt Romney Effect." Romney is conventional Mormon genealogically. His roots are in the Mountain West. But he was raised in Michigan, and spent much of his adult life in Massachusetts. I suspect with Mormons there is a much milder version of what has gone on with the Indian American community: strong selection biasing on migrants toward achievers. This gives Americans a skewed view of what Indians are like. While half of Indian Americans have graduate degrees, 1/3 of Indians are illiterate! How's that for a difference? Similarly,bi-coastal Americans don't meet many Mormons, and the ones they do are more likely to be achievers, not those of more downscale or modest means who never left St. George, Utah.