Circular flow of income

Model of the real economy

The circular flow of income or circular flow is a model of the economy in which the major exchanges are represented as flows of money, goods and services, etc. between economic agents. The flows of money and goods exchanged in a closed circuit correspond in value, but run in the opposite direction. The circular flow analysis is the basis of national accounts and hence of macroeconomics. The idea of the circular flow was already present in the work of Richard Cantillon. François Quesnay developed and visualized this concept in the so called Tableau économique. Important developments of Quesnay's tableau were Karl Marx's reproduction schemes in the second volume of Capital: Critique of Political Economy, and John Maynard Keynes' General Theory of Employment, Interest and Money. Richard Stone further developed the concept for the United Nations (UN) and the Organisation for Economic Co operation and Development to the system, which is now used internationally.

The circular flow of income is a concept for better understanding of the economy as a whole and for example the National Income and Product Accounts (NIPAs). In its most basic form it considers a simple economy consisting solely of businesses and individuals, and can be represented in a so called "circular flow diagram." In this simple economy, individuals provide the labour that enables businesses to produce goods and services. These activities are represented by the green lines in the diagram. Alternatively, one can think of these transactions in terms of the monetary flows that occur. Businesses provide individuals with income (in the form of compensation) in exchange for their labor. That income is spent on the goods and services businesses produce. These activities are represented by the blue lines in the diagram above.]] One of the earliest ideas on the circular flow was explained in the work of 18th century Irish French economist Richard Cantillon, Cantillon described the concept in his 1730 Essay on the Nature of Trade in General, in chapter 11, entitled "The Par or Relation between the Value of Land and Labor" to chapter 13, entitled "The Circulation and Exchange of Goods and Merchandise, as well as their Production, are Carried On in Europe by Entrepreneurs, and at a Risk." Thornton eds. (2010) further explained:
Cantillon develops a circular flow model of the economy that shows the distribution of farm production between property owners, farmers, and workers. Farm production is exchanged for the goods and services produced in the cities by entrepreneurs and artisans. While the property owners are “independent,” the model demonstrates the mutual interdependence between all the classes of people that Adam Smith dubbed the “invisible hand” in The Theory of Moral Sentiments (1759). Cantillon distinguished at least five types of economic agents: property owners, farmers, entrepreneurs, labors and artisans, as expressed in the contemporary diagram of the Cantillon's Circular Flow Economy. by which the initial conditions necessary for economic activity to occur are constantly re created. Economic reproduction involves the physical production and distribution of goods and services, the trade (the circulation via exchanges and transactions) of goods and services, and the consumption of goods and services (both productive or intermediate consumption and final consumption). Karl Marx developed the original insights of Quesnay to model the circulation of capital, money, and commodities in the second volume of Das Kapital to show how the reproduction process that must occur in any type of society can take place in capitalist society by means of the circulation of capital. Marx distinguishes between "simple reproduction" and "expanded (or enlarged) reproduction". In the former case, no economic growth occurs, while in the latter case, more is produced than is needed to maintain the economy at the given level, making economic growth possible. In the capitalist mode of production, the difference is that in the former case, the new surplus value created by wage labour is spent by the employer on consumption (or hoarded), whereas in the latter case, part of it is reinvested in production.

An important development was John Maynard Keynes's 1933 publication of the General Theory of Employment, Interest and Money. Keynes' assistant Richard Stone further developed the concept for the United Nations (UN) and the Organisation for Economic Co operation and Development to the systems, which is now used internationally. The first to visualize the modern circular flow of income model was Frank Knight in 1933 publication of The Economic Organization. Knight (1933) explained:

[we may view the] economic organization as a system of prize relations. Seen in the large, free enterprise is an organization of production and distribution in which individuals or family units get their real income, their "living," by selling productive power for money to "business units" or "enterprises", and buying with the money income thus obtained the direct goods and services which they consume. This view, it will be remembered, ignores for the sake of simplicity the fact that an appreciable fraction of the productive power in use at any time is not really employed in satisfying current wants but to make provision for increased want satisfaction in the future; it treats society as it would be, or would tend to become, with progress absent, or in a "static" state. Knight pictured a circulation of money and circulation of economic value between people (individuals, families) and business enterprises as a group, explaining: "The general character of an enterprise system, reduced to its very simplest terms, can be illustrated by a diagram showing the exchange of productive power for consumption goods between individuals and business units, mediated by the circulation of money, and suggesting the familiar figure of the wheel of wealth."

A circular flow of income model is a simplified representation of an economy. (Some sources refer to households as "individuals" or the "public" and to firms as "businesses") The model assumes that there is no financial sector, no government sector, and no foreign sector. In addition, the model assumes that (a) through their expenditures, households spend all of their income on goods and services or consumption and (b) through their expenditures, households purchase all output produced by firms.

The circular flow diagram is an abstraction of the economy as a whole. The diagram suggests that the economy can reproduce itself. The idea is that as households spend money of goods and services from firms, the firms have the means to purchase labor from the households, which the households to then purchase goods and services. Suggesting that this process can and will continuously go on as a perpetual motion machine. However, according to the Laws of Thermodynamics perpetual motion machines do not exist. The First Laws says matter and energy cannot be created or destroyed, and the Second Laws says that matter and energy move from a low entropy, useful, state towards a less useful higher entropy state. Thus, no system can continue without inputs of new energy that exit as high entropy waste. Just as no animal can live on its own waste, no economy can recycle the waste it produces without the input of new energy to reproduce itself. The economy therefore cannot be the whole. It must be a subsystem of the larger ecosystem. This is not to say that the circular flow diagram isn't useful in understanding the basics of an economy, such as leakages and injections. However, it cannot be ignored that the economy intrinsically requires natural resources and the creation of waste that must be absorbed in some manner. The economy can only continue churning if it has matter and energy to power it and the ability to absorb the waste it creates. This matter and low entropy energy and the ability to absorb waste exists in a finite amount, and thus there is a finite amount of inputs to the flow and outputs of the flow that the environment can handle, implying there is a sustainable limit to motion, and therefore growth, of the economy.