Marginal utility

Carl Menger (1840-1921), an Austrian economist stated the basic principle of marginal utility in Grundsätze der Volkswirtschaftslehre^[55] (1871, Principles of Economics). Consumers act rationally by seeking to maximise satisfaction of all their preferences. People allocate their spending so that the last unit of a commodity bought creates no more than a last unit bought of something else. Stanley Jevons (1835-1882) was his English counterpart, and worked as tutor and later professor at Owens College, Manchester and University College, London. He emphasised in the Theory of Political Economy (1871) that at the margin, the satisfaction of goods and services decreases. An example of the theory of diminishing returns is that for every orange one eats, the less pleasure one gets from the last orange (until one stops eating). Then Leon Walras (1834-1910), again working independently, generalised marginal theory across the economy in Elements of Pure Economics (1874). Small changes in people's preferences, for instance shifting from beef to mushrooms, would lead to a mushroom price rise, and beef price fall. This stimulates producers to shift production, increasing mushrooming investment, which would increase market supply and a new price equilibrium between the products - e.g. lowering the price of mushrooms to a level between the two first levels. For many products across the economy the same would go, if one assumes markets are competitive, people choose on self interest and no cost in shifting production.

Early attempts to explain away the periodical crises of which Marx had spoken were not initially as successful. After finding a statistical correlation of sunspots and business fluctuations and following the common belief at the time that sunspots had a direct effect on weather and hence agricultural output, Stanley Jevons wrote,

"when we know that there is a cause, the variation of the solar activity, which is just of the nature to affect the produce of agriculture, and which does vary in the same period, it becomes almost certain that the two series of phenomena— credit cycles and solar variations—are connected as effect and cause.^[56]