Top: Pasta/soup aisle ~8.5 feet across | Bottom: Cereal aisle ~7.5 feet across
The next time you are at Target, count the number of floor tiles across the cereal aisle or candy aisle and then count the tiles on any other food aisle. The candy aisle and cereal aisle are a foot narrower than the other food aisles. I'd assume it's so parents can't keep kids from grabbing items on those aisles no matter how centered they set the cart. The parents are then more likely to buy the item to prevent a tantrum from the child when the child sees the item being taken from then and put back on the shelf. That's all well and good, but Wal-Mart doesn't narrow these aisles. I've measured.
Why wouldn't Wal-Mart take advantage of this if it is to increase sales? Why does Target do this if it doesn't really increase sales? Maybe my theory is wrong and it's not about increased sales, but nothing is random in store design. What advantage does Target get from this and why does Wal-Mart not want/get that same advantage? I don't have answers, but it sure is annoying when you have more than two people going down the cereal aisle at the same time.
The frozen food aisles are the widest in the store, but that makes sense because it leaves room for the doors to be opened on both sides and still allow people to pass.
(the difference in angles on these two photos adds to the narrowing effect, it doesn't look that dramatic in person, but there is a physical difference you can see when you are there even without measuring the width)