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Complexity economics is the application of complexity science to the problems of economics. It relaxes several common assumptions in economics, including general equilibrium theory. While it does not reject the existence of an equilibrium, it sees such equilibria as "a special case of nonequilibrium", and as an emergent property resulting from complex interactions between economic agents. [1] [2] [3] The complexity science approach has also been applied to computational economics. [4]
The "nearly archetypal example" is an artificial stock market model created by the Santa Fe Institute in 1989. [5] The model shows two different outcomes, one where "agents do not search much for predictors and there is convergence on a homogeneous rational expectations outcome" and another where "all kinds of technical trading strategies appearing and remaining and periods of bubbles and crashes occurring". [5]
Another area has studied the prisoner's dilemma, such as in a network where agents play amongst their nearest neighbors or a network where the agents can make mistakes from time to time and "evolve strategies". [5] In these models, the results show a system which displays "a pattern of constantly changing distributions of the strategies". [5]
More generally, complexity economics models are often used to study how non-intuitive results at the macro-level of a system can emerge from simple interactions at the micro level. This avoids assumptions of the representative agent method, which attributes outcomes in collective systems as the simple sum of the rational actions of the individuals. It also takes into account the view of emergence in economics.
Physicist César Hidalgo and Harvard economist Ricardo Hausmann introduced a spectral method to measure the complexity of a country's economy by inferring it from the structure of the network connecting countries to the products that they export. The measure combines information of a country's diversity, which is positively correlated with a country's productive knowledge, with measures of a product ubiquity (number of countries that produce or export the product). [6] [7] This concept, known as the "Product Space", has been further developed by MIT's Observatory of Economic Complexity, and in The Atlas of Economic Complexity [7] in 2011.
The economic complexity index (ECI) introduced by Hidalgo and Hausmann [6] [7] is highly predictive of future GDP per capita growth. In Hausmann, Hidalgo et al., [7] the authors show that the List of countries by future GDP (based on ECI) estimates ability of the ECI to predict future GDP per capita growth is between 5 times and 20 times larger than the World Bank's measure of governance, the World Economic Forum's (WEF) Global Competitiveness Index (GCI) and standard measures of human capital, such as years of schooling and cognitive ability. [8] [9]
Sapienza physicist Luciano Pietronero and collaborators have recently proposed a different approach. [10] [11] [12] These metrics are defined as the fixed point of non-linear iterative map. Differently from the linear algorithm giving rise to the ECI, this non-linearity is a key point to properly deal with the nested structure of the data. The authors of this alternative formula claim it has several advantages:
The metrics for country fitness and product complexity have been used in a report [13] of the Boston Consulting Group on Sweden growth and development perspectives.
Brian Arthur, Steven N. Durlauf, and David A. Lane describe several features of complex systems that they argue deserve greater attention in economics. [14]
Complexity economics has a complex relation to previous work in economics and other sciences, and to contemporary economics. Complexity-theoretic thinking to understand economic problems has been present since their inception as academic disciplines. Research has shown that no two separate micro-events are completely isolated, [16] and there is a relationship that forms a macroeconomic structure. However, the relationship is not always in one direction; there is a reciprocal influence when feedback is in operation. [17]
Complexity economics has been applied to many fields.
Complexity economics draws inspiration from behavioral economics, Marxian economics, institutional economics/evolutionary economics, Austrian economics and the work of Adam Smith. [18] It also draws inspiration from other fields, such as statistical mechanics in physics, and evolutionary biology. Some of the 20th century intellectual background of complexity theory in economics is examined in Alan Marshall (2002) The Unity of Nature, Imperial College Press: London. See Douma & Schreuder (2017) for a non-technical introduction to Complexity Economics and a comparison with other economic theories (as applied to markets and organizations).
The theory of complex dynamic systems has been applied in diverse fields in economics and other decision sciences. These applications include capital theory, [19] [20] game theory, [21] the dynamics of opinions among agents composed of multiple selves, [22] and macroeconomics. [23] In voting theory, the methods of symbolic dynamics have been applied by Donald G. Saari. [24] Complexity economics has attracted the attention of historians of economics. [25] Ben Ramalingam's Aid on the Edge of Chaos includes numerous applications of complexity economics that are relevant to foreign aid.
In the literature, usually chaotic models are proposed but not calibrated on real data nor tested. However some attempts have been made recently to fill that gap. For instance, chaos could be found in economics by the means of recurrence quantification analysis. In fact, Orlando et al. [26] by the means of the so-called recurrence quantification correlation index were able detect hidden changes in time series. Then, the same technique was employed to detect transitions from laminar (i.e. regular) to turbulent (i.e. chaotic) phases as well as differences between macroeconomic variables and highlight hidden features of economic dynamics. [27] Finally, chaos could help in modeling how economy operate as well as in embedding shocks due to external events such as COVID-19. [28]
For an updated account on the tools and the results obtained by empirically calibrating and testing deterministic chaotic models (e.g. Kaldor-Kalecki, [29] Goodwin, [30] Harrod [31] ), see Orlando et al. [32]
According to Colander (2000), Colander, Holt & Rosser (2004), and Davis (2008) contemporary mainstream economics is evolving to be more "eclectic", [33] [34] diverse, [35] [36] [37] and pluralistic. [38] Colander, Holt & Rosser (2004) state that contemporary mainstream economics is "moving away from a strict adherence to the holy trinity – rationality, selfishness, and equilibrium", citing complexity economics along with recursive economics and dynamical systems as contributions to these trends. [39] They classify complexity economics as now mainstream but non-orthodox. [40] [41]
In 1995-1997 publications, Scientific American journalist John Horgan "ridiculed" the movement as being the fourth C among the "failed fads" of "complexity, chaos, catastrophe, and cybernetics". [5] In 1997, Horgan wrote that the approach had "created some potent metaphors: the butterfly effect, fractals, artificial life, the edge of chaos, self organized criticality. But they have not told us anything about the world that is both concrete and truly surprising, either in a negative or in a positive sense." [5] [42] [43]
Rosser "granted" Horgan "that it is hard to identify a concrete and surprising discovery (rather than "mere metaphor") that has arisen due to the emergence of complexity analysis" in the discussion journal of the American Economic Association, the Journal of Economic Perspectives . [5] Surveying economic studies based on complexity science, Rosser wrote that the findings, rather than being surprising, confirmed "already-observed facts." [5] Rosser wrote that there has been "little work on empirical techniques for testing dispersed agent complexity models." [5] Nonetheless, Rosser wrote that "there is a strain of common perspective that has been accumulating as the four C's of cybernetics, catastrophe, chaos, and complexity emerged, which may now be reaching a critical mass in terms of influencing the thinking of economists more broadly." [5]
Chaos theory is an interdisciplinary area of scientific study and branch of mathematics focused on underlying patterns and deterministic laws of dynamical systems that are highly sensitive to initial conditions, and were once thought to have completely random states of disorder and irregularities. Chaos theory states that within the apparent randomness of chaotic complex systems, there are underlying patterns, interconnection, constant feedback loops, repetition, self-similarity, fractals, and self-organization. The butterfly effect, an underlying principle of chaos, describes how a small change in one state of a deterministic nonlinear system can result in large differences in a later state. A metaphor for this behavior is that a butterfly flapping its wings in Texas can cause a tornado in Brazil.
Neoclassical economics is an approach to economics in which the production, consumption, and valuation (pricing) of goods and services are observed as driven by the supply and demand model. According to this line of thought, the value of a good or service is determined through a hypothetical maximization of utility by income-constrained individuals and of profits by firms facing production costs and employing available information and factors of production. This approach has often been justified by appealing to rational choice theory.
A complex system is a system composed of many components which may interact with each other. Examples of complex systems are Earth's global climate, organisms, the human brain, infrastructure such as power grid, transportation or communication systems, complex software and electronic systems, social and economic organizations, an ecosystem, a living cell, and ultimately the entire universe.
This aims to be a complete article list of economics topics:
Business cycles are intervals of general expansion followed by recession in economic performance. The changes in economic activity that characterize business cycles have important implications for the welfare of the general population, government institutions, and private sector firms. There are numerous specific definitions of what constitutes a business cycle. The simplest and most naïve characterization comes from regarding recessions as 2 consecutive quarters of negative GDP growth. More satisfactory classifications are provided by, first including more economic indicators and second by looking for more informative data patterns than the ad hoc 2 quarter definition.
An economic model is a theoretical construct representing economic processes by a set of variables and a set of logical and/or quantitative relationships between them. The economic model is a simplified, often mathematical, framework designed to illustrate complex processes. Frequently, economic models posit structural parameters. A model may have various exogenous variables, and those variables may change to create various responses by economic variables. Methodological uses of models include investigation, theorizing, and fitting theories to the world.
Econophysics is a non-orthodox interdisciplinary research field, applying theories and methods originally developed by physicists in order to solve problems in economics, usually those including uncertainty or stochastic processes and nonlinear dynamics. Some of its application to the study of financial markets has also been termed statistical finance referring to its roots in statistical physics. Econophysics is closely related to social physics.
A macroeconomic model is an analytical tool designed to describe the operation of the problems of economy of a country or a region. These models are usually designed to examine the comparative statics and dynamics of aggregate quantities such as the total amount of goods and services produced, total income earned, the level of employment of productive resources, and the level of prices.
Computational economics is an interdisciplinary research discipline that involves combines methods in computational science and economics to solve complex economic problems. This subject encompasses computational modeling of economic systems. Some of these areas are unique, while others established areas of economics by allowing robust data analytics and solutions of problems that would be arduous to research without computers and associated numerical methods.
Heterodox economics is any economic thought or theory that contrasts with orthodox schools of economic thought, or that may be beyond neoclassical economics. These include institutional, evolutionary, feminist, social, post-Keynesian, ecological, Austrian, Humanistic economics, complexity, Marxian, socialist, and anarchist economics.
Mainstream economics is the body of knowledge, theories, and models of economics, as taught by universities worldwide, that are generally accepted by economists as a basis for discussion. Also known as orthodox economics, it can be contrasted to heterodox economics, which encompasses various schools or approaches that are only accepted by a minority of economists.
William Arnold Barnett is an American economist, whose current work is in the fields of chaos, bifurcation, and nonlinear dynamics in socioeconomic contexts, econometric modeling of consumption and production, and the study of the aggregation problem and the challenges of measurement in economics.
Statistical finance, is the application of econophysics to financial markets. Instead of the normative roots of finance, it uses a positivist framework. It includes exemplars from statistical physics with an emphasis on emergent or collective properties of financial markets. Empirically observed stylized facts are the starting point for this approach to understanding financial markets.
Dynamic stochastic general equilibrium modeling is a macroeconomic method which is often employed by monetary and fiscal authorities for policy analysis, explaining historical time-series data, as well as future forecasting purposes. DSGE econometric modelling applies general equilibrium theory and microeconomic principles in a tractable manner to postulate economic phenomena, such as economic growth and business cycles, as well as policy effects and market shocks.
John Barkley Rosser Jr. was a mathematical economist and Professor of Economics at James Madison University in Harrisonburg, Virginia since 1988. He was known for work in nonlinear economic dynamics, including applications in economics of catastrophe theory, chaos theory, and complexity theory. With Marina V. Rosser he invented the concept of the "new traditional economy". He introduced into economic discourse the concepts of chaotic bubbles, chaotic hysteresis, and econochemistry. He also invented the concepts of the megacorpstate and hypercyclic morphogenesis. He was the first to provide a mathematical model of the period of financial distress in a speculative bubble. With Marina V. Rosser and Ehsan Ahmed, he was the first to argue for a two-way positive link between income inequality and the size of an underground economy in a nation. Rosser's equation has been used to forecast ratios of future Social Security benefits to current ones in real terms.
Mathematical economics is the application of mathematical methods to represent theories and analyze problems in economics. Often, these applied methods are beyond simple geometry, and may include differential and integral calculus, difference and differential equations, matrix algebra, mathematical programming, or other computational methods. Proponents of this approach claim that it allows the formulation of theoretical relationships with rigor, generality, and simplicity.
The Goodwin model, sometimes called Goodwin's class struggle model, is a model of endogenous economic fluctuations first proposed by the American economist Richard M. Goodwin in 1967. It combines aspects of the Harrod–Domar growth model with the Phillips curve to generate endogenous cycles in economic activity unlike most modern macroeconomic models in which movements in economic aggregates are driven by exogenously assumed shocks. Since Goodwin's publication in 1967, the model has been extended and applied in various ways.
Disequilibrium macroeconomics is a tradition of research centered on the role of disequilibrium in economics. This approach is also known as non-Walrasian theory, equilibrium with rationing, the non-market clearing approach, and non-tâtonnement theory. Early work in the area was done by Don Patinkin, Robert W. Clower, and Axel Leijonhufvud. Their work was formalized into general disequilibrium models, which were very influential in the 1970s. American economists had mostly abandoned these models by the late 1970s, but French economists continued work in the tradition and developed fixprice models.
Duncan K. Foley is an American economist. He is the Leo Model Professor of Economics at the New School for Social Research and an External Professor at the Santa Fe Institute. Previously, he was Associate Professor of Economics at MIT and Stanford, and Professor of Economics at Columbia University. He has held visiting professorships at Woodrow Wilson School at Princeton University, UC Berkeley, and Dartmouth College, as well as the New School for Social Research.
Charles Frederick Roos was an American economist who made contributions to mathematical economics. He was one of the founders of the Econometric Society together with American economist Irving Fisher and Norwegian economist Ragnar Frisch in 1930. He served as Secretary-Treasurer during the first year of the Society and was elected as President in 1948. He was director of research of the Cowles Commission from September 1934 to January 1937.