Jevons succeeded in bringing together the separate elements of utility theory into a coherent theory of value and exchange in his main work (Theory of Political Economy, 1871). Although he only analyzes the side of demand and excludes the treatment of supply, his work is one of the pillars, with that of Menger and Leon Walras, subjects on whom the marginalist revolution falls. It is interesting to mention that Jevons did not know, while writing his work, the works of the forerunners and even less those of Gossen, whose problems were very close to his own.
In the early 1870s, he published an elaborate synthesis of the theories of consumption, exchange, and distribution. With that utility can only be measured in ordinal terms and that the utility provided by a good is inversely proportional to the amount of that good previously owned. He clearly establishes the difference between total utility and what he called "final degree of utility," which was later called "marginal utility." In addition to this great contribution, I also develop a hypothesis about income, interest and capital productivity, among other topics. The use of mathematics stems from methodological evidence: it is necessary to adjust to the nature of the object of study and the tool to measure the constant variations of the economy is the integral calculus. After discovering Cournot,Jevons, for example, reproaches him for drawing demand curves without establishing their foundations.
Theory of marginal utility in Jevons
Holding that utility is the pleasure derived from the use of a product, and that the most important law of all economics is the tendency to satiety. It states that utility tends to decrease as the quantity used increases.
It expresses by means of a fractional equality the principle that, no person in an exchange by means of the barter in the market of two agricultural products will be satisfied, unless the quotient of the marginal utilities between them is inversely proportional to their exchange quotient.
The commercial body and the law of indifference
The commercial body, according to Jevons definition, is formed by the sum of buyers and sellers in the market of a single merchandise in a truly competitive market Jevons, (1998: 128). The law of indifference refers to the existence of a single price for a certain merchandise in that competitive market.
Jevons developed a theory of the supply of labor based on the concept of marginal utility. For Jevons work consists of any painful effort of the mind and body partially or totally experienced with a view to obtaining a future good Jevons, 1871 (1998: 183) In other words, work is: the exchange between a present good (penalties from work) for obtaining a future good (the income commonly called salary); This concept rather refers to a net balance between the pain that work produces (especially that which requires physical effort) and the pleasure that results from not working (resting) and; the job offer is considered to be piece rate.
"The Jevons Paradox"
Also called the Rebound Effect, it states that as technological improvement increases the efficiency with which a resource is used, an increase in the consumption of said resource is more likely than a decrease. Jevons' observation is not a paradox from the point of view of Logically, but in economics it is considered a paradox because it opposes the economic intuition that improved efficiency allows people to use less of a resource.
The end of William Stanley Jevons was tragic. Throughout his life he had many illnesses that forced him to spend long periods of time healing in spas. Curiously, he did not die a victim of his delicate health, but drowned in a pool at one of these spas. With his death, at age 47, several unfinished books remained. Authors maintain that WS Jevons was an individual who laid the foundations on the economic policies that today we call Neoliberals.
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