Someone brought this to my attention yesterday and I was amazed. I'm guilty of buying this brand of sugar simply because it is less expensive than the 5 lb. bag of Domino sugar in Wal*Mart.
Now I'm quite sure Wal*Mart has done everything correct with the pricing and all the info we need to know is on the shelf sticker and the weight is clearly marked on the bag. 
My friend and I just never noticed. We assumed the 4 lb. bag of Great Value Pure Sugar was a 5 lb. bag.
Does anyone know if this was ever a 5 lb. bag?
Breyers icecream did this a good while back. Have you noticed the same thing happening in other foods?
