Neoclassical synthesis (NCS) refers to an economic doctrine that appeared in the U.S. in the early 1940s, and would remain the dominant paradigm until the late 1960s, when monetarism took over. It was Paul Samuelson, in his book “Economics”, 1955, who gave this doctrine its sense of synthesis, since it can be described as Keynesian in the short run and neoclassical in the long run. This is, policy makers will be able to adjust the economy (especially using fiscal policies, seen by NCS’ economists as far more effective than monetary policy) in the short run, but considering also that equilibrium will be reached in the long run without the need for public intervention. Theoretical and empirical studies by NCS’ economists are mainly based on the IS-LM model and the Phillips curve.

The IS-LM model was first developed by John Hicks in 1937 and Hansen expanded and popularized it in 1949. It is built on the premises put forward by J. M. Keynes in his “General theory”, 1936, and gives fiscal policy a higher degree of efectiveness (IS-LM policies effects, NCS view).

The Phillips curve, derived from an empirical study, gave a relationship between unemployment and inflation, which was not explicit in Keynes’ analysis. The validity of this relationship has been highly criticized by different schools of economic thought, such as monetarism, the New Classical Macroeconomics and the New Keynesian Economics.

Other renowned NCS’ economists are Modigliani, for his analysis of consumption under an intertemporal utility maximization frame, known as the life-cycle hypothesis; Jorgenson, for his work on the investment function; and Tobin and Baumol, for their studies on the demand and supply of money.

The NCS as a macroeconomic mainstream started struggling in the late 1960s, following a high inflation episode in the U.S., which could not be explained using the theoretical framework of this doctrine. Not long after, in the mid-1970s, stagflation in the U.S. meant the rise of monetarism and the subsequent fall of the NCS.

This school of economic thought, which focuses on macroeconomics, is mainly based on interpretations of John Maynard Keynes’ most important book, the “General Theory of Employment, Interest and Money”, 1936.

Keynes’ main thesis was that unemployment during the Great Depressionwas the result of a decreasing demand, and that the solution was to revive the economic system through public investment. A Keynesian policy would be one that promotes, for example, public works such as building dams or highways.

Supporters of Keynesianism, or Keynesian economics, believe that although businesses and private sector entities working on a liberal environment function in an efficient way, sometimes market failures may appear. For this, they support a certain degree of implication by the public sector in order to prevent these failures and restore the economy if they appear, through fiscal and monetary policies. However, they will give more credit to the former, the latter being more supported by Monetarists.

Keynesianism was the main economic doctrine from 1936 until the advent of Monetarism, with which it coexisted until the stagflation of the seventies.

Joan Robinson, Nicholas Kaldor and John R. Hicks, are just some of the great disciples of Keynes, and therefore Keynesian economists, mainly from the Cambridge School in its not neoclassical meaning, to name a few.

Name given to British economist Alfred Marshall and his followers, who were also part of the neoclassical school of economics, such as Arthur C. Pigou and Francis Y. Edgeworth, which fully assimilated the concepts and methods of marginalism.

They are also considered to be part of the Cambridge school, although in other terms not relating to neoclassical economics, the group of economists which in one way or another collaborated with J. M. Keynes in the thirties and forties, partly in connection with the problems of war. These include Post-Keynesian economists Joan Robinson and Nicholas Kaldor, extending the group to the Neo-Keynesians John R. Hicks, Paul A. Samuelson and James Tobin.

Keynes was a British economist (1883-1946), son of the economist and methodologist John Neville Keynes. J. M. Keynes first gained notoriety with his work during the Versailles Peace Conference, when he cleverly proposed in his book “The Economic Consequences of the Peace”, 1919, not to punish Germany to avoid future retaliation. Later, during the Great Depression, he fought the conservative views advocating for a restoration of the gold standard in the famous pamphlet “The Economic Consequences of Mr. Churchill”. After a series of papers on monetary issues, he published in 1936 the most important of his works, the “General Theory of Employment, Interest and Money”, which was the foundation of the then called New Economic Science, or Keynesianism. Keynes’ main thesis was that unemployment during the Great Depression was the result of the decrease in effective demand. Therefore, to achieve full employment, it was necessary to revive the economic system through public investment. In the last years of his life, J. M. Keynes participated in the negotiations of Bretton Woods, in 1944, leading to the creation of the International Monetary Fund.

At the Bretton Woods conference, where he was part of the British delegation, he raised the idea that the IMF should be constituted as a true worldwide central bank, capable of issuing paper currency for international payments, for which he proposed the name “bancor”. Most of the ideas mentioned in the “Keynes Plan” were not followed through, since they competed with the U.S. proposals specified in the “White Plan”.

Great disciples of Keynes, part of the Cambridge School, were Joan Robinson, Nicholas Kaldor and John R. Hicks, to name a few.

Irving Fisher was an American economist (1867-1947), professor of Political Economy at Yale University, known for his contributions to quantitative economics (works such as “The Nature of Capital and Income”, 1906, and “The Purchasing Power of Money”, 1911) and especially the development of index numbers. He also addressed interest rates, in his opinion governed by two interacting forces: the impatience of individuals in terms of exchanging future income for current income, and the principle of yield paid by doing so. In his “Appreciation and interest”, 1896, Fisher showed the relation between the nominal interest rate (i), the real interest rate (r) and inflation (Π) using an equation, known nowadays as the Fisher equation:

i ≈ r + Π

Although this relation derived from earlier works by Jacob de Haas, Irving Fisher’s formula is an easier way to represent this relation.

In the early autumn of 1929, shortly before the famous Black Thursday, Irving Fisher said, “stock prices have reached what looks like a permanently high plateau.” After the stock Crash, he lost his credibility, being this the reason why his work was not taken seriously until decades later.

Predecessor of monetarism, and following the works of bullionists, David Hume, the School of Salamanca and John Stuart Mill, he showed that prices vary depending on the volume of money in circulation, being this variation as shown by the equation of exchange, which he first depicted in his book “The Purchasing Power of Money“.

Pareto was an economist and sociologist of Italian origin, born in Paris (1848-1923), who taught at the University of Lausanne, as well as previously did his mentor, Léon Walras. They both were part of the Lausanne School, which is considered, along with the Austrian School, as the birthplace of marginalism and neoclassical economics.

His chief works were “Course of Political Economy”, 1896-97, and “Manual of Political Economy”, 1906. Among Pareto’s contributions, we can highlight the graphical development of Edgeworth box, as well as an improvement on the way indifference curves are drawn, and studies on the personal distribution of income.

In his studies of the late nineteenth century, Pareto found some regularity in the personal distribution of income in different countries. From that regularity, he determined a series of economic and sociological conclusions, which became known afterwards as Pareto’s Laws. He also studied some regularities in businesses, where concentration was the explanation for the fact that many companies get 80% of their revenue from only 20% of its products.

Nowadays, however, he is mostly known for the Pareto optimal, a notion widely used in game theory and welfare economics.

Pigou was a British economist (1877-1959), disciple of Alfred Marshall, whom he succeeded as a professor at Cambridge. Pigou is remembered above all as a precursor of welfare economics, for his books “Wealth and Welfare”, 1912, and “The Economics of Welfare”, 1920, in which he used measures of national income and its distribution in order to understand how wealth and welfare are related. He is also remembered for making a distinction between different degrees of price discrimination.

Being part of the Cambridge school, Pigou used common tools derived from neoclassical economics, such as marginalism, amongst others.

Edgeworth was an Irish economist (1845-1926), professor of Political Economy at the University of Oxford, whose most important contributions to economic science were statistical in nature, primarily in the area of index numbers, highlighting also the mathematical apparatus needed for the drawing of indifference curves and the contract curve, from the first analysis of W.S. Jevons. Although it would be Vilfredo Pareto, in 1906, who would draw an indifference map, as we know the representation of various indifference curves nowadays.

In his “Mathematical Psychics: an Essay on the Application of Mathematics to the Moral Sciences”, published in 1881, Edgeworth designed what is now known as an Edgeworth box, which basically allows us to compare two mathematical functions represented as curves using the same axis. However, it was also Pareto in 1906 who would depict this Edgeworth box as we know it, as a “box”. It was also in “Mathematical Psychics” where utility functions started to be written as F(x_n, y_n, z_n), closer to what we see in today’s textbooks. It must be said, as an anecdotical fact, that Edgeworth mentioned in a footnote this book, when interpreting an earlier book form J. J. Thomson, that “energy is the product of mass and the square of velocity”, which is generally attributed to Einstein or other physicists.

In 1894, Edgeworth published a diagram in “Theory of International Values” explaining the terms of trade from a geometrical perspective, basing this article on J. S. Mill‘s work on trade and his theory on reciprocal demand.

Alfred Marshall was an English economist (1842-1924), and the true founder of the neoclassical school of economics, which combined the study of wealth distribution of the classical school with the marginalism of the Austrian School and the Lausanne School. Professor at Cambridge, he was the author of “Principles of Economics”, 1890, which became the most widely read manual in microeconomics in his time. This book, which is his major work, established a radical change on how economics were taught. Instead of just writing long pages, Marshall draw diagrams throughout the chapters, allowing a better understanding of economic theories and models, such as J. S. Mill’s reciprocal demand, or an analysis on the differences between fixed and variable cost, and the importance of time periods when analyzing these matters. In fact, Marshall is the precursor of today’s cost analysis.

Of unquestionable educational clarity and filled with profound social principles, Marshall contributed to economic science with concepts such as elasticity and the further development of other subjects, surpluses for instance. Although he did not invent the term nor did he initiate this theory, he did made a clearer separation and definition of different kind of surpluses, such as consumer’s and producer’s surplus.

Also in his “Principles of Economics”, he stated the differences between internal and external economies of scale, as well as a diagram which depicted the fluctuations in supply and demand that took place before arriving to a steady state, a general equilibrium. This equilibrium was reached by means of changing amounts, not prices, as Léon Walras stated.

He is also considered as founder of the Cambridge School, where he taught economics until his retirement. Other renowned economists belonging to this school are Arthur C. Pigou and J. M. Keynes.

Léon Walras, a French economist (1834-1910), is considered, along with W. S. Jevons and Carl Menger, a co-founder of marginalism and theory of utility. He is regarded as the founder, along with Pareto, of the Lausanne School. On his “Elements of Pure Economics”, 1874, Walras made his major contribution to economics, general equilibrium theory, on which all demands are interrelated into a coherent set of relationships.

This general equilibrium was reached by means of a “tâtonnement”, changes in price that would gradually approximate supply and demand until a steady statewas reached. A few decades later, Alfred Marshall would present a different general equilibrium theory, on which the steady state would be reached by means of changes in quantities.