Do you have a source for that? I'd be interested in reading more about it. I never would have guessed credit transactions would be that low at Walmart; I grew up in a poor, "redneck" area and knew a lot of people (my family included) that depended on the "float" you get with a credit card to give a little flexibility over their normal paycheck-to-paycheck existence. But I'd believe the data, if it exists for public consumption.
I'm curious what searches have you done to find such data. Companies like Netspend (just acquired this week by TSYS) and Greendot exist almost exclusively to serve this market. American Express has their own offering called Bluebird card to compete in the same market. There are lots of articles discussing these companies and the target market of the "unbanked" when looking for info on these public companies. The only reason I hesitate to post links to specifics is because I'd rather not taint your approach to finding such information, but it is pretty easy to find, if you are to search.
