Inventory management is vitally important to organizations, because inventory sitting idly on the shop floor or in the warehouse costs money. Many years ago, a firm’s wealth was measured by its inventory. Today inventory is recognized as an unproductive asset in cost-conscious firms. Dollars not tied up in inventory can be used in other productive ventures. Keeping inventory low is especially important for high-tech firm, because so many of their products lose value quickly as they are replaced by more innovative and lower-cost models. For example, the value of a completed personal computer falls rapidly; even if space for PCs were free, a company would lose money on its PC inventory. Service firms are concerned with inventory too, which is a big part of the reason for the growth of RFID, as described earlier.