I work for a national brand name underwear company, and there are always conversations around here picking apart the customer demographics of the 'Big 3' retailers. Sometimes I get amused by how much scrutiny goes into determining what type of person shops where based on income, age, race, geography, etc.
Personally, I do shop at all three and I don't believe it is all that scientific. I do prefer Target for items such as clothing and home essentials (bedding, towels, decor, ectc). Our Target store is also cleaner and easier to access than our WalMart. However, I do all of my grocery shopping at Walmart and tend to go there for basic things such as toiletries and medications. I do despise going there because of the hassle of the traffic and waiting in the long checkout lines, but the lower prices outweigh the hassle at times. I would have to say that I shop at Kmart the least amount of all. I go in there when I am in a hurry (it is closer to my work and home than the other two) and only need a few things. I can also find good deals on baby items there at times.
I guess the point I'm trying to make it that so much emphasis is put on trying to categorize people and create profiles of consumers. But, sometimes I think it has more to do with specific circumstances and not how much money you make or what race you are, etc. Where do you shop?