The investment made by this firm is a planned inventory investment - that is, a stock change. If the firm wants to keep as few unsold winter tires as possible in its stocks until the month of February, and there are still unsold winter tires in February when it comes, this is an unplanned inventory investment. Unplanned stock changes can be regarded as a sign showing that sales are not as good as expected and that there is too much production in the previous period.