Stock rotation
Stock rotation is a way of mitigating stock loss. It is the practice, used in hospitality and retail, especially in food stores such as restaurants and supermarkets, of moving products with an earlier sell-by date to the front of a shelf (or in the cooler if the stored item is on repack so they get worked out before the new product), so they get picked up and sold first, and of moving products with a later sell-by date to the back. In the case of food, a food rotation system that organizes and rotates food cans on a first-in first-out basis (FIFO) is important for storing food to prevent foodborne illness and to control commercial kitchen costs. When used correctly, the first-in first-out food rotation method ensures serving safe food and eliminates spoiled food waste. An alternative method promoted by the World Health Organization is First-Expiry, First-Out (FEFO). Here, goods are rotated out by the earliest expiry to further minimize expiry loss and spoilage. Description 
Most, if not all, packaged products, will have either a sell by date on them or a display until date; in practice, these are exactly the same thing. After this date, it is either illegal for the store to sell them (this is the case in Ireland) or the quality will have deteriorated to the point at which nobody will buy them. In either case, they cannot be sold. If a product is still on shelves after its sell by date, it will have to be thrown away, which is both costly and wasteful to the store (suppliers must be paid even if stock is not sold). Therefore, it is imperative that sell by dates are strictly adhered to, and that products which will perish earlier be sold as quickly as possible. Shoppers, on the most part, will simply walk up to a shelf and take the front most box of the product they are looking for; this is especially true if they are in a hurry. They will generally also, unless they are specifically looking for a product that will last longer, not pay much attention to sell by/use by dates. If products with an early sell by date are at the front, and later ones at the back, they will be sold first. If things are organized the other way round, or stock is improperly rotated, newer stock will be sold first, leaving out of date stock sitting on the shelves which will have to be thrown away. Rotation also applies to loose products; in this case, there is usually no set sell by date, and produce must merely look fit to eat. Older stock is merely placed on top of newer stock to rotate it. Problems 
Some customers are fully aware of the practice of rotation, and will reach towards the back of the shelf in order to get newer (and therefore slightly better) produce. Also, when applied to large amounts of produce, rotation can be difficult if not impossible. It only takes one careless worker to disrupt rotation and create problems. Other methods of stock loss mitigation 
If a stock is nearing its sell by date, stock may be reduced; its price is lowered in order to be more appealing to customers. Reduced stock is usually included in the rotation of stock, and is therefore moved to the front of the shelf ahead of any unreduced stock. See also
 Inventory turnover rate

References

Retail processes and techniques