Should milk be priced at $2.00 or $6.00 per gallon, or for that matter at any other price? What determines the value of milk? Recently at least one observer has stated opposition to the proposed price collar “compact plus” policy because it doesn’t reflect the “full value” of milk. Well, when is milk undervalued? Economics has another name. It is often appropriately called the theory of value. Over the past 200 years different economists have advanced different general economic or value theories. David Ricardo, in the early 19th century, proffered what is now called the Ricardian or Classical Theory of Value. In a classical economy prices are determined by the costs of production. Ricardo talked of three: rent for land, wages for labor, and profits for capital. Marx unsuccessfully tried to convince the world that there is one input, labor, and that all value comes from it: the labor theory of value.