I sense a little playfulness in your question.
I heard a funny line recently.
Why are there no Walmarts in China? There are no Mexicans there.
If I see your avatar by an answer, I always make an attempt to read your response. They are usually logical and witty.
Larger return lines could mean more impulse buying for which there is a larger return ratio. Ten causes of this for different areas could be:
a) better advertising techniques,
b) lower self-control for that population as a rule,
c) better economy,
d) community as a whole hates Walmart and causes harm to the company in anyway possible,
e) cheap cr@p from China that has to be returned,
f) mom and dad are a little more obese than a month ago and the stuff just don't fit,
g) gifts from Walmart are repetitive purchases and need to be returned,
h) after you receive your welfare funds, wear new clothes the first of the month then return them to restock the food supplies for the second part,
i) buying a $16 DVD player and expecting features such as stereo out or auxiliary inputs and expecting it to work for more than a month.
j) kids sneak stuff into the cart or use the credit card without permission,
and finally,
k) some people just get bored from drinking a beer every time the bug zapper zaps!
We keep it real. In my area, we have no expectations of high quality or of high performance from the cheapest place in town. Walmart return lines are mostly empty except for holidays. I shop Walmart all the time.
