Larger Marketplaces
In a free market encompassing larger numbers of people, individuals continue to act in accordance with their personal value scales, which give rise to supply and demand. Consequently, supply and demand are not "impersonal" economic forces as popularly imagined, but an expression of human beings seeking values to satisfy their personal ends. For instance, suppose that Smith initially has 3 cows and 100 hens. Let us examine his behavior in a market where cows are bartered for hens.

By the law of diminishing marginal utility (pp. 4.4:29-31), Smith's first cow has greater utility to him than his second cow, which in turn has greater utility than his third cow. His third cow has greater utility than a fourth cow that he might purchase, and so on. Smith's behavior in this market depends not only on the utilities of his cows, however, but also on the utility he attaches to the hens for which they are traded. A price of 26 hens, for instance, will clearly have more subjective utility to him than a price of 25 hens, and so on. (We assume, of course, that cows and hens are both scarce goods.) As Smith acquires more cows, each cow becomes successively less useful (valuable) to him. At the same time, as he gives up hens in exchange for the cows, each hen becomes more useful (valuable) to him.