That book sounds like one you need to read....
Lets examine what I said...
Per Capita Income
... By definition Per Capita Income takes all income within a given population and divides it equally among the entire population.
You came back with...
Median Household Income
...By definition Median Household Income divides the income of each household into 2 equal groups one high and one low with the 50th percentile income being the median income.
If you want to use Median Household Income for the figure that is fine with me. Median Household Income: $146,755 trumps the $25,417 fairly hard and yes the expenses of operating a business in that area are much higher and so are the costs.
ZIPskinny demographic information for 06820 - DARIEN CONNECTICUT
Use your dot graph all you want and you might depending on your sampling get a reasonably close US average, but the bottom line is what plumbers in your area are willing to do the work for.
Schools out! For tonights homework read the first 2 chapters in "On Being Certain: Believing You Are Right Even When You're Not" and we will have a quiz tomorrow.