> Of course, the number of classes depends on our interests. So for
> instance, many sensibly observe the US as a monolithic economic
> powerhouse. Whereas marketing professionals might distinguish zillions
> of classes.
In fact, you can find out which of those zillions of classes you're most likely to belong to using this rudimentary, free version of Prizm market segmentation software:
http://www.claritas.com/MyBestSegments/Default.jsp?ID=20&SubID=&pageName=ZIP%2BCode%2BLook-up