The ACS (I'm largely using the 2012 five-year estimates here) has this data - with households divided into ten income brackets - but it doesn't get visualized frequently because it's hard to show ten quantities on a map. So I wanted to calculate a standard deviation for wealth in each county and find census tracts that had high and low incomes with low variance.
I used family income because it better represents actual wealth and poverty - household and individual incomes include too many college students, young professionals with low incomes but few expenses, etc. The problem with doing a standard deviation here is that the difference between making $25,000 a year and making $75,000 a year is a lot bigger than the difference between making $150,000 a year and $200,000. So instead of using actual dollar numbers, I used the census bureau's ten categories - weighted one through ten. Those categories - and the statewide distribution of families among them - can be seen in this histogram:
So a standard deviation of "2" means the data tends to be distributed two income brackets in either direction.
On this map, I've pulled out the census tracts that have a standard deviation below 1.85 and 2.1, representing relatively little variation. In green are the tracts with a median family income over $80,000. In red are the tracts with a median family income under $50,000. There is a clear trend - suburban areas around the major metro areas are where wealth is concentrated, while inner city areas, as well as rural southwest and southside Virginia are more likely to have more concentrated poverty. Tracts in gray have either a more typical median income or more spread-out distribution.
I've also mapped the standard deviation by county. Blue counties have a narrower distribution of incomes, while red counties have more variation. As you might expect, cities lean towards a wider range of incomes, while counties tend to have more homogeneity. But those cities and counties at the top and bottom have a wide range of median family incomes.
Here are the top and bottom counties for variance (citizens in a wide range of income brackets):
One last thing piqued my interest. Which counties have an income distribution that most resembles the statewide income spread? Refer to the first graph in this post for the statewide numbers.
I calculated the variance for each county and came up with the following map:
If your county is darker, it means the income distribution of the state is well-represented. If lighter, it means there is a significant difference between the state and the county. Henrico County and Charlottesville City take the top spots as being most representative. High on the list are Manassas, Virginia Beach, Albemarle, and Chesterfield Counties. Charlottesville would be much different if I was using individual income (or even household income) thanks to the high number of university students and young professionals.
Here's Henrico and Charlottesville's histograms alongside the Commonwealth's. Virginia is in blue, Henrico is in red, and Charlottesville is in green.:
Bringing up the rear are Falls Church and Emporia, with Grayson County, Arlington, Loudoun County, Patrick County, Martinsville, and others close behind. Here's Falls Church's and Emporia's incomes next to the state's. The state is in blue still. I don't think I need to tell you which city is which...
