Even if a company uses sophisticated technology to control inventory, the accounting measures do not have to reflect precise physical flows, as would occur using specific identification. Rather, the LIFO, FIFO, and weighted average methods refer to assumptions that are made about the flow of inventory through the company. Using FIFO, the company assumes that the first goods sold are the oldest and the most recently acquired items remain in inventory on the balance sheet. Using LIFO, the costs of the oldest inventory are maintained on the balance sheet under the assumption that the most recently acquired inventory is sold first. The weighted average method uses average costs over the reporting period to calculate the inventory balance.