And, particularly in the retail sector, inventories of some goods - like clothing and cars - can spur sales because customers have the chance to try out different sizes or option packages before buying. With so many reasons for holding inventories, inventory investment may appear about as difficult to predict as investment in equipment or structures. It is probably even more difficult.
So far I have mentioned only the reasons for which businesses intentionally change their inventory holdings. But inventory swings are often the result of miscalculations on the part of business owners. If a particular product is unexpectedly popular, inventories get drawn down; if the product is unpopular, inventories pile up.