Purchasing power (sometimes retroactively called adjusted for inflation) is the number of goods or services that can be purchased with a unit of currency. For example, if one had taken one unit of currency to a store in the 1950s, it is probable that it would have been possible to buy a greater number of items than would today, indicating that one would have had a greater purchasing power in the 1950s. Currency can be either a commodity money, like gold or silver, or fiat currency, or free-floating market-valued currency like US dollars. As Adam Smith noted, having money gives one the ability to "command" others' labor, so purchasing power to some extent is power over other people, to the extent that they are willing to trade their labor or goods for money or currency.