The color scale on this map distorts one's perception of where there are significant differences. There are sharp color boundaries at arbitrary points on a color scale and counter-intuitive gradations of color (while greens reflect the driest counties, the darkest green is actually the least dry of the greens). With a more continuous color scale this map would seem a lot less dramatic.
Agreed, the differences aren't as stark as the map seems. Almost all of the states fall between 15% and 25% percent of the population.
Wisconsin stands out at 25.29% of the population labeled as excessive drinkers due to the large amount of dark red, but South Dakota is at 22.43% -- less than 3% difference, but that state is mostly orange.
For a county example, Hardin, TX is 19.13% and Rusk, WI is 20.82%. A difference of just under 1.7%, but the Wisconsin county is bright red and the Texas county is orange.
