The harvest reaches the market after the work has been done. The seed has been planted, the field tended, the crop gathered. Buyer and seller meet over something that already exists. Their agreement can put it to a more valuable use, but the grain on the table has a history that their exchange alone cannot explain. This gives the surplus a second beginning. One account starts with the alternatives the parties can improve by trading. Another starts with the means that had to be used to produce anything they could trade. Both ask what is left over. They subtract different things.
The production account first asks whether the process can begin again. A harvest that must all be returned to seed, maintenance, and the support of those doing the work can reproduce its conditions without leaving a remainder for other uses. Sraffa opens Production of Commodities by Means of Commodities with an economy of this kind: industries exchange the products needed to replace the inputs they have used. The relations between them are material before they are monetary. Wheat and iron must arrive in the necessary quantities. An exchange ratio that leaves one industry unable to replace its inputs cannot reproduce the stipulated system, however profitable another industry may appear in isolation.
Suppose a small economy produces one hundred baskets of grain in a year. Twenty must be retained as seed and fifty assigned to the stipulated maintenance of its workers; assume these are the only inputs, with no trade, inventory change, or other capital to replace. Thirty baskets remain. If the next harvest is only seventy, the same requirements leave none. The arithmetic identifies a physical residual under the stated conditions. It has yet to tell us who receives it. Nor has it established that fifty baskets are a timeless measure of what workers require or should obtain. That quantity is part of the example’s social and technical arrangement. A different provision for workers would change the remainder without changing the number of baskets harvested.
With many goods, even the size of the residual becomes a harder question. A ton of iron and a bushel of wheat cannot be added into a single physical total. Their money value requires prices, and in Sraffa’s surplus system the prices and the common rate of profit are determined together. The value of the inputs cannot simply be announced first and then used to explain a return whose determination also affects those values. He also makes wages capable of including a share of the surplus, rather than fixing workers permanently at subsistence. The production account therefore opens a question about distribution within the conditions of reproduction. It does not award the entire remainder to whoever happens to own the inventory at the end of the year.
Marx gives the remainder a different and sharper account. The employer purchases labor-power, the worker’s capacity to work for a period. The value of that capacity and the value created by its exercise need not coincide. In his analysis, the means of production transfer their value to the product, while living labor adds new value; the working day can continue after the worker has produced the equivalent of the value of labor-power. The balance is surplus-value. This argument depends on his theory of value and the social organization of production. It is more specific than the observation that revenue exceeds the wage bill, and it is concerned with something different from a buyer’s pleasure at finding a bargain.
The distinction allows equal exchange and surplus-value to coexist within the argument. The employer can pay the stipulated value of labor-power and purchase the materials at their values, yet obtain a product containing more value than the total advanced. The explanation lies in what happens during production. Marx does not need to begin by alleging that a merchant has deceived a customer or that a wage promise has been broken. His question is how the purchaser acquires command over the use of a capacity whose exercise can produce more than the value paid for it. The ownership of that capacity’s product, and the conditions under which the worker must sell it, enter the inquiry before the finished commodity reaches its buyer.
Take a ten-hour day in this theoretical account, with six hours of socially necessary labor equivalent to the value of labor-power and four hours beyond it. The ratio of surplus labor to necessary labor is four to six, or two-thirds. It is not four to ten. The latter measures the surplus portion as a fraction of the whole day; Marx’s rate of surplus-value compares it with the necessary portion. Nor is the rate a profit return on the entire value of machinery, materials, and wages advanced. These distinctions matter because changing the denominator changes the question. The working day need not be physically split into six hours making the worker’s food and four making the employer’s goods. It is an analytical division of the new value produced.
The exchange account needs another set of numbers. Suppose a buyer would pay thirty for an object and the relevant resource opportunity cost of producing and delivering it is twenty. Hold other effects and income effects aside. A sale at twenty-five leaves five with the buyer and five with the seller: ten in combined gains over those stipulated alternatives. A sale at twenty-two leaves eight and two. The price divides the same interval differently. Nothing in these figures tells us how many hours of necessary or surplus labor Marx’s account would assign to the object. Conversely, the ten-hour division does not tell us the buyer’s maximum willingness to pay. The two computations cannot be converted into each other merely because each contains a remainder.
A more productive method can enlarge that exchange interval. If it lowers the resource cost from twenty to fifteen while leaving the buyer’s valuation at thirty, the available gain rises from ten to fifteen. A price change alone, with the cost and valuation fixed, does not have that effect. Yet the new method may also alter the length or intensity of work, the equipment required, and the incomes of the people displaced or retained. The gain in one transaction is an incomplete account of those changes. A production inquiry follows the resources and social relations that made the cheaper object possible; an exchange inquiry follows the alternatives improved by its availability. The importance of either inquiry is diminished when its answer is made to stand for both.
The physical remainder is also distinct from the gain made possible by exchange. Two people can begin with fixed stocks and benefit from swapping what each values less for what each values more. No additional basket need be harvested for their opportunities to improve. Equally, a larger harvest can leave the gains concentrated among people whose claims are secure, while those who worked it obtain little more. Production, allocation, and distribution are connected, but their changes need not move in step. A useful account must say which of them has changed and what comparison establishes the improvement.
The account begins with what must be replaced and continues with who can claim what remains.
The Residue and The Unpaid bring the source of the surplus back into view. They make the finished sale answer to the process that preceded it. The exchange account, in turn, asks what people can do with the resulting goods and which alternatives they surrender. Keeping these questions distinct gives each its force. It also prepares the final question of The Yardstick: what justifies treating the remainder, however carefully defined, as a measure of how well a society is doing? The argument remains open.