Weighted-average

When a company uses the weighted-average method and prices are rising, its cost of goods sold is less than that obtained under LIFO, but more than that obtained under FIFO. Inventory is not as badly understated as under LIFO, but it is not as up-to-date as under FIFO. Weighted-average costing takes a middle-of-the-road approach. A company can manipulate income under the weighted-average costing method by buying or failing to buy goods near year-end. However, the averaging process reduces the effects of buying or not buying.

The four inventory costing methods, specific identification, FIFO, LIFO, and weighted-average, involve assumptions about how costs flow through a business. In some instances, assumed cost flows may correspond with the actual physical flow of goods. For example, fresh meats and dairy products must flow in a FIFO manner to avoid spoilage losses. In contrast, firms use coal stacked in a pile in a LIFO manner because the newest units purchased are unloaded on top of the pile and sold first. Gasoline held in a tank is a good example of an inventory that has an average physical flow. As the tank is refilled, the new gasoline mixes with the old. Thus, any amount used is a blend of the old gas with the new.