It has been a while, but only because I have more exhaustive detail then ever before:

So when I did the political correlation for all of those Western states, I also did the high school/college numbers. And then, having those numbers, I also had the Colorado numbers, from previously. I added the Utah numbers in, and ended up with a bunch of data points. All the data points together showed something to me: that data entry is a lovely and fun hobby. They also showed me this:There are 297 data points there. I didn't bother labeling many of them. I did label Denver, because it is a major metropolitan area, and also because its unusual place shows that it has a pattern different from most of what you would find in the Western States. This type of (relatively) high-college, low-highschool speaks of an urban area that attracts less skilled workers, and is more common in the urbanized east than in the Western states.What is most interesting about this diagram for me is that there aren't a lot of outliers. And that it has a specific shape. For some reason, in my mind, not a lot of outliers would make more sense on an X=Y curve. In this case, we have this complicated crescent pattern, that seems to hold true across 297 counties in seven states.
One of the things I wondered is if this was actually several different graphs layed out on each other. Did the three parts of the crescent represent three different types of counties?
So what I did was sort these counties by "Rural Urban Continuum" code. This is a set of codes put out by the Economic Research Service of the USDA that sorts counties by how urban and rural they are. As with any demographic measure, they are not perfect, but they are a useful tool.
So here is the plot for counties in metropolitan areas of some sort, define as RUC codes 1-3
There is a lot of diversity in these counties, since some "metropolitan" counties can be fairly small in population. After all, the summit of Mt. Hood is a "metropolitan" area by this reckoning. In other words, Owyhee County and King County maybe shouldn't belong in the same plot.
But! Despite the fact that this diagram is more spread out, the shape remains. The four counties in the upper right are also not the most urbanized counties. By contrast, the three counties that are the most urbanized (Denver, King, Multnomah) all hang to the left, because like most urban counties, they have lots of college graduates, but also attract less educated workers as well.

So next we will look at counties with codes from 4 to 7: counties that are not metropolitan, but have some urban population. As with above "some urban population" can mean many different things.

Two things here: although once again the picture is somewhat blurred, it is also again, vaguely crescent shaped. Secondly, there is pretty big gap in this diagram. Most of the counties seem to be bunched up right below the 20% mark for college graduation, with a few over 20%. Then, between 30 and 40%: only two counties. Above 40%, there is a lot of counties showing up. From what I know about those counties over 40%, they seem to be mostly resort communities. Gallatin, Montana, for example, is the county adjacent to Yellowstone Park, and so has had a big influx of wealthy residents in the past few decades.

Finally, lets look at the truly rural counties, those considered to have no urban population whatsoever: codes 8 and 9.


And once again...crescent. In fact, if I do say so myself, this is the prettiest of all the crescents we have seen so far. I can't think of anything particularly interesting to say about this crescent, besides its pretty, and how about those San Juans?