If this doesn't show you the disparity amongst cities and towns. . . Take a look at this slide show that Boston.com has shared with its readers:
It opens with "Over the past 30 years, Sherborn’s median household income, adjusted for inflation, has increased more than 40 percent to nearly $190,000, while the median income in Lawrence has dropped 20.1 percent to $36,573, according to US Census statistics."
The 20 highest and lowest towns are depicted in this presentation.
Lenny, on Twitter @product19