That's why I like the Neighborhood Walmarts. The computer tracks all that. Their business model is to have 100% turnover of perishable items in 14 days, and 100% turnover of non-perishable items in 21 days. If a product doesn't turn over that quickly, they know, and they won't carry it anymore. Now, employees can make mistakes. I watched a lady try and buy a 6 pack of some Mexican beer I had never heard of, and it wouldn't ring up. Manager came over, went to the shelf, then the office and came back and said "we pulled this brand off the shelves yesterday because it wasn't selling, and an employee must have put it back out by mistaken, I'm afraid I can't sell it to you".
Walmart is hard core.