Where are the non-academic PhD chemists in the United States? Where aren't they?

Here's an interesting visualization of the geography of industrial (or at least non-academic) chemistry, from The Chronicle of Higher Education:

Two things to explain here that I think I understand about these charts:

• The darker the state is, the higher the absolute number of non-academic Ph.D. physical scientists.
• The selected states have the highest (or lowest) rate of chemists amongst non-academic Ph.D. physical scientists. 

Here's the raw numbers, in order of "prevalence index", a number that's not explained in the chart:

Chemists most prevalent: Delaware: 7.836, New Jersey: 2.459, Indiana: 1.475, North Carolina: 1.393, Michigan: 1.115, Kentucky: 0.721, Arkansas: 0.607

Chemists least prevalent: North Dakota: 0.2620, Nevada: 0.2620, New Hampshire: 0.3110, New Mexico: 0.3440, South Dakota: 0.4260, Mississippi: 0.4780, Vermont: 0.5740, Idaho: 0.7700, Wyoming: 0.7700, Montana: 0.8360, Alaska: 0.8690. 

I'm not positive that this chart showed me anything I didn't know (I probably would not have guessed Kentucky or Arkansas, but that's about it.) That said, it's worth a click.