Bar code labels have made a huge impact on the retail industry that once had to rely on hand counts to know how much of each product was left in inventory. Not only was this method time-consuming, it wasn't always accurate as it relied on the work people. That is not to say computers are infallible, but when you rely on humans to do a count, many distractions can affect the accuracy of the count. Bar code labels allow the store to set up their system so that every scanned product will be deducted from inventory. In many cases stores also configure a re-order point so that they don't have to make a decision about how much merchandise to keep on hand and when to order more.
The problem that is obvious with bar code labels in controlling inventory is that many stores do not utilize it to its fullest potential. When used properly, there is no reason a customer should go to a store and not have the merchandise on hand except for rare instances when the store had a sale and more of the sale items were sold than projected. Warehouse workers should be scanning bar code labels when new merchandise comes in so that stores know what they have in inventory, but often this is the only thing that is being scanned, thus leaving the store thinking it has more on hand than it does. If all retailers were to utilize bar code labels to the extent of their capabilities, we would rarely find a product out of stock.
With bar code labels so readily available, it's difficult to understand why retailers do not use them to control inventory coming and going. It is not difficult, and it would certainly increase their flow of traffic because customers would know that they would always be able to purchase the products they need without having to wait for the next shipment of products from the warehouse.