In theory, COGS should include the cost of all inventory that was sold during the accounting period. In practice, however, companies often don’t know exactly which units of inventory were sold. Instead, they rely on accounting methods such as the first in, first out (FIFO) and last in, first out (LIFO) rules to estimate what value of inventory was actually sold in the period. If the inventory value included in COGS is relatively high, then this will place downward pressure on the company’s gross profit. For this reason, companies sometimes choose accounting methods that will produce a lower COGS figure, in an attempt to boost their reported profitability.