Quantifying A/B/C/D-type Neighborhoods?

[Shane Wilhelm]

I'm familiar with the idea of visiting a property and getting a 'feel' for the neighborhood types, but how can you back that up with hard data, or at the very least, concrete observations?

Crime rates? 
Police officers per capita? 
Median income?
Ratio of Whole Foods to Walmarts? 

In what ways do you personally quantify the division between these neighborhood types?