 But while labor power is just like any other commodity in terms of how its price is determined, it is unique in one very importance respect. Labor, and labor alone, according to Marx, has the capacity to produce value beyond that which is necessary for its own reproduction. In other words, the value that goes into the commodities that sustain a worker for a twelve-hour work day is less than the value of the commodities that worker can produce during those twelve hours. This difference between the value a worker produces in a given period of time and the value of the consumption goods necessary to sustain the worker for that period is what Marx called surplus value.