It may be only five numbers long, but a zip code can say a lot about a person. Like if they have rich neighbors, for example. Of 29,000 zip codes examined by the Internal Revenue Service, only three had an average yearly income of one million dollars or more, based on recently released data from 2008 (h/t Tax.com). But the average income per year for all of the top ten richest zip codes exceeds $700,000, according to IRS data, a staggering sum compared to the average American taxpayer's income of just $49,000 in 2009.

http://www.huffingtonpost.com/2012/02/23/richest-zip-codes-in-america_n_1297611.html