What concept is illustrated when a shopper leaves a store without purchasing an out-of-stock item?

The concept illustrated when a shopper leaves a store without purchasing an out-of-stock item is best captured by the idea of a lost sale. This term refers to instances where potential sales revenue is lost because the desired product is unavailable at the time of the buyer's decision to purchase. When customers encounter stockouts, they not only miss the opportunity to complete their transaction, but they may also choose to seek the product elsewhere, leading to a further loss of business for the retailer.

In a supply chain context, lost sales can directly impact a company's revenue and forecasts, as they indicate that demand exists for a product that the company failed to meet due to inventory issues. This highlights the importance of effective inventory management practices to ensure that products are available when customers want to buy them, thereby maximizing sales and customer satisfaction.