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Richard H. Day was a renaissance man and a difference maker. This essay honors the life and scholarly work of Dick Day, expressed mostly through those who knew him as colleagues and students. It also provides an introduction to this special issue, which honors Professor Day with papers of the type he founded this journal to publish. [ABSTRACT FROM AUTHOR]

In this paper, we review the theories of business cycles in the 20th century after the work of John Maynard Keynes. Fluctuations in economic activity have been observed with considerable regularity since the beginning of the last century, motivating empirical efforts to, identify, measure, and understand business cycles, contributing to the identification of stylized facts on business cycles, facts the business cycle theories should try to explain. Theories however have been very distinct through the years. Despite the different explanations for the sources of cycles, in mainstream economics, there was the underlying hypothesis of stability and equilibrium as a main characteristic of the economic system. The heterodox view on business cycles, in contrast, starts with Keynes pre-dynamic theory, considering the intrinsic instability of the system and extends through several other authors and theories. In this paper, we use the concepts of equilibrium and instability as a demarcating guide to separate theories in two groups: the mainstream view and the heterodox view. We notice however that, even though different authors and theories might share similar views on the self-equilibrating property of the economic system, there is no coherent integration between similar theories. We conclude the paper with some methodological insights that might lead to a coherent and integrated approach to explain business cycles in the heterodox view, requiring new and complex methods and tools. • Equilibrium and instability as demarcating guide to Business Cycles theories. • Empirical stylized facts on Cycles are to be explained by theories. • In mainstream, cycles are external shocks damped by internal response mechanisms. • The heterodox view instead assumes endogenous instability. • Despite common assumptions, cycle theories have been very distinct. • We propose an integrated heterodox approach under some guiding principles. [ABSTRACT FROM AUTHOR]

• We consider the requirement of taking climate action for authorities in urban mobility planning. • Three alternative small-scale projects that the city planners can develop and implement are used. • Twelve societal dynamics criteria are grouped as technical, environmental, economic, and political. • We propose an improvement of WASPAS by Einstein norms in a fuzzy environment over triangular fuzzy numbers. • The results show that the best plan should be inclusive, equitable and economically efficient. The twin challenges posed by biodiversity loss and climate change compel public authorities to transform their traditional policies to take climate action via urban mobility planning. However, the interests of the stakeholders may differ so that the development and the implementation of the required action become challenging. In this study, we trace how an optimal action plan should take the societal dynamics into account and how the actions taken can reshape the societal dynamics. To illustrate and analyze the complex forces that drive the decision-making process in urban mobility planning, we develop a scenario, which bunches three small-scale urban mobility planning alternatives that are frequently proposed in the literature and practiced in cities. Alternatives are assessed under twelve criteria reflecting economic, environmental, technical, and political dimensions of the decision problem. In solving the problem, we propose an improvement of the Weighted Aggregated Sum Product Assessment (WASPAS) approach by applying Einstein norms in a fuzzy environment over triangular fuzzy numbers to evaluate and rank the prioritization of climate change mitigation strategies. The proposed method comprises two stages. In the first stage, the weight coefficients of the criteria are calculated. In the second stage, the fuzzy Einstein WASPAS approach is applied to select the most suitable alternative among the three alternatives. Testing and validation of the model are done through a comparison with existing decision making methods in the literature. The results show that the best plan should be inclusive and equitable as well as economically efficient. Although the economic dimension is highly significant to the decision-making process, choosing the most suitable urban mobility planning option requires the consideration of other societal dynamics, too. [ABSTRACT FROM AUTHOR]

• Introduces a novel morphogenetic framework for understanding economic dynamics • Presents a unified approach to study the interplay between economic structures and their dynamics • Highlights the role of coupling, diffusion and symmetry-breaking in studying structural change • Synthesises interdisciplinary insights from three different disciplines, and develops prospective links with economic theorising Economic systems are characterised by constant change and evolution, and explanations concerning the properties of economic structures have received sustained interest. The structure of a system and its dynamics can influence each other through feedback effects. In this paper we offer a brief survey of how structure plays a role in dynamic economic theory – in particular, growth and business cycles. We propose a morphogenetic framework, inspired from the creation of forms in developmental biology, as a potential unifying approach for studying economic structures and their dynamics. We synthesise insights from three different strands of research, focusing on the role of coupling, diffusion and symmetry-breaking. We highlight their existing and prospective links with economics. [ABSTRACT FROM AUTHOR]

In this paper we study the duopoly model proposed by M. Kopel [26], where two firms compete “ a la Cournot ” and the reaction curves have a higher degree of coupling in the sense that firms have to make their choices simultaneously. We will make a descriptive analysis of the two-dimensional model, making an approach through particular situations. On the other hand, when the firms are homogeneous a one-dimensional invariant subset is present in the model. We will give an analytical proof of the existence of a (topological) chaotic behavior for a wide range of parameter values and we will study when chaotic synchronization and collusion occur. [ABSTRACT FROM AUTHOR]

Capitalist economic systems display a wide variety of oscillatory phenomena whose underlying causes are often not well understood. In this paper, I consider a very simple model of the reciprocal interaction between investment, capacity utilization, and their time derivatives. The model, which gives rise periodic oscillations, predicts qualitatively the phase relations between these variables. These predictions are observed to be consistent in a statistical sense with econometric data from the US economy. [ABSTRACT FROM AUTHOR]

On average, environmental income accounts for more than a quarter of rural household income in tropical and sub-tropical countries. One way to increase incomes from wild-harvested products is cultivation. In a landmark paper, Homma (1992) identified four phases describing the economic dynamics of environmental product cultivation, emphasising product scarcity. We reviewed literature that applied and/or discussed Homma's model. This suggested that additional factors, beyond resource scarcity, induce the transition to cultivation. We propose an alternative model of the dynamics of environmental product cultivation pathways, emphasising stock size, contextual, harvester, and mediating factors. The model has four possible product-level outcomes: scarcity induced cultivation, economic extinction, abundance with cultivation, and continued sole wild harvesting. We investigated this model empirically through the case of commercial medicinal plant harvesting in Nepal, using harvester interviews (n = 362) and published monthly price data for the most commonly traded products (n = 12) during a nine-year period. We found evidence of all four possible product-level outcomes, with "abundance with cultivation" being the most common. This supports that scarcity is not sufficient to explain cultivation processes; harvester decision-making processes and contextual and mediating factors must also be assessed. • The first systematic review of Homma's model of extractive reserves. • New model of the economic dynamics of environmental product cultivation pathways. • Outcomes: scarcity induced cultivation, extinct, abundant with/without cultivation. • All four outcomes documented in empirical case. • Harvester characteristics are significant for whether cultivation is undertaken. [ABSTRACT FROM AUTHOR]

Renewable energy has been encouraged to address climate change and promote sustainable development, leading to structural changes in the national energy matrices. Brazil is reaching a 50/50 renewable/non-renewable energy mix. However, the wide variability in emissions intensity among renewable sources raises questions about the effectiveness of structural changes for SDGs. The present study aims to identify typological profiles (TPs) of structural changes in sectoral energy and carbon footprint and their contributions to sustainable development. From an ecological input-output model, we calculated the sectoral energy and carbon footprint for 2000, 2005, 2010, and 2015. The method adds novelty by creating typologies of structural changes confronting renewable vs. non-renewable and mainly renewable vs. renewable. Four TPs of structural change were found. TP-I and TP-II tended to increase the relative share of renewables in their energy footprint, opposing TP-III and TP-IV. A controversy emerged contrasting TP-I and TP-II since both increased renewable consumption. TP-I decreased the renewable emissions while TP-II increased them. The explanation lies in the energy sources' emissions intensity. While TP-I sectors tended to increase the consumption of renewable energies with low intensity of emissions, such as electricity, TP-II sectors increased the consumption of renewables whose gross emissions intensity could be even higher than non-renewables. Therefore, the simple substitution of non-renewable for renewable sources may not be enough. Pursuing the long-term sustainable structural changes need to be planned based on renewable sources with the lowest net emission intensity and highest renewability. [Display omitted] • Replacing non-renewables with renewables may not be enough to achieve the SDGs. • Typological profiles (TPs) of structural changes may indicate the most effective strategies. • Effective pro-SDGs strategies move sectors from TP-IV, TP-III, and TP-II to TP-I. • Renewables with the lowest net emissions intensity and highest renewability are preferable. • Being renewable is not enough when the emission intensity is higher than non-renewables. [ABSTRACT FROM AUTHOR]

In this paper we investigate the economic dynamics of a seven-equation model of the business cycle. The main distinctive features of the model are related to: (a) the role played by the public sector in redeploying income between workers and capitalists, since it is assumed that the bargaining power of the two classes affects tax rates and transfers levied upon them; (b) the influence that past events have on the agents’ current behavior, with particular regard to consumption patterns; (c) the specification of firms’ investment function, which incorporate Keynesian and Harrodian elements by assuming that investments are a function of both the difference between interest and profit rate and the discrepancy between actual and desired capital to output ratio. Since all these assumptions imply possible balance sheets disequilibrium, particular regard is dedicated to the analysis of macroagents’ debt dynamics. Special emphasis is placed on the analysis of the destabilization of equilibria via Hopf bifurcations, which leads to the emergence of an interesting and rich cyclical dynamics. [ABSTRACT FROM AUTHOR]

Abstract: We study the global attractors of quasi-linear non-autonomous difference equations and we apply the reached results to an economic growth model of Solow type while assuming that the population growth rate is endogenous and described by the logistic equation. [Copyright &y& Elsevier]

Abstract: The aim of this paper is to investigate whether an oligopoly given by isoelastic demand function and constant marginal costs converges to a duopoly, that is, all the firms except for two of them will not produce anything in future. [Copyright &y& Elsevier]

Abstract: This work is primarily based on a recently proposed toy model by Thurner et al. (2010) on Schumpeterian economic dynamics (inspired by the idea of economist Joseph Schumpeter ). Interestingly, punctuated equilibrium has been shown to emerge from the dynamics. The punctuated equilibrium and Power law are known to be associated with similar kinds of biologically relevant evolutionary models proposed in the past. The occurrence of the Power law is a signature of Self-Organised Criticality (SOC). In our view, power laws can be obtained by controlling the dynamics through incorporating the idea of feedback into the algorithm in some way. The so-called ‘feedback’ was achieved by introducing the idea of fitness and selection processes in the biological evolutionary models. Therefore, we examine the possible emergence of a power law by invoking the concepts of ‘fitness’ and ‘selection’ in the present model of economic evolution. [Copyright &y& Elsevier]

Abstract: This paper studies the impacts on economic growth of a small tourism-driven economy caused by an increase in the growth rate of international tourism demand. We present a formal model and empirical evidence. The ingredients of the dynamic model are a large population of intertemporally optimizing agents and an AK technology representing tourism production. The model shows that an increase in the growth of tourism demand leads to transitional dynamics with gradually increasing economic growth and increasing terms of trade. In our empirical application, an econometric methodology is applied to annual data of Antigua and Barbuda from 1970 to 2008. We perform a cointegration analysis to look for the existence of a long-run relationship among variables of economic growth, international tourism earnings and the real exchange rate. The exercise confirms the theoretical findings. [ABSTRACT FROM AUTHOR]

Abstract: Studies of non-linear cobweb models have failed to address a fundamental issue: whether the complex dynamical behavior displayed by such models is consistent with the survival of producers. This paper shows that where borrowing is unconstrained, as is implicitly assumed in standard cobweb models, borrowing results in financial crises. Incorporating constraints on borrowing is needed to salvage cobweb models. Industry performance (in terms both of profitability and of the incidence of bankruptcies) is highly sensitive to the nature of such credit restrictions. [Copyright &y& Elsevier]

Abstract: Extreme events are one of the main channels through which climate and socioeconomic systems interact, and it is likely that climate change will modify the probability distribution of the losses they generate. The long-term growth models used in climate change assessments, however, cannot capture the effects of such short-term shocks. To investigate this issue, a non-equilibrium dynamic model (NEDyM) is used to assess the macroeconomic consequences of extreme events. This exercise allowed us to define the economic amplification ratio, as the ratio of the overall production loss due to an event to its direct costs. This ratio could be used to improve the cost–benefit analysis of prevention measures. We found also that, unlike a Solow-like model, NEDyM exhibits a bifurcation in GDP losses: for each value of the capacity to fund reconstruction, GDP losses remain moderate if the intensity and frequency of extremes remain under a threshold value, beyond which GDP losses increase sharply. This bifurcation may partly explain why some poor countries that experience repeated natural disasters cannot develop. Applied to the specific issue of climate change, this model highlights the importance of short-term constraints in the assessment of long-term damages, and shows that changes in the distribution of extremes may entail significant GDP losses in absence of specific adaptation. It suggests, therefore, that to avoid inaccurately low assessments of damages, researchers must take into account the distribution of extremes instead of their average cost and make explicit assumptions on the organization of future economies. [Copyright &y& Elsevier]

Abstract: We consider a new property of an optimal control problem called a lens. A lens is an interior point in the state–control phase plane where—given the value of the state variable—there is only one control value satisfying the necessary optimality conditions and—given the value of the control variable—there is only one state value satisfying the necessary optimality conditions. We build a simple model that generates a lens and give necessary and sufficient conditions under which a lens occurs. [Copyright &y& Elsevier]

Abstract: A simple model of pure competition among a finite number of cautious, adaptive economizing firms is used to explore industrial behavior when outputs are bounded by financial feedback. Identical agents share identical trajectories that can converge to a competitive equilibrium, but the slightest heterogeneity in initial conditions, degree of caution, or in unit costs drives all from the market except a subset of competitors who share identical costs and output levels. Those remaining can converge to a competitive equilibrium. If demand is inelastic at such a point, however, fluctuations in output, perhaps after a prolonged period of profitable growth can arise with profitable periods followed by sharp losses or even a complete collapse. [Copyright &y& Elsevier]

Abstract: Chaos in foreign exchange markets is a common issue of concern in the study of economic dynamics. In this work, we mainly investigate the competition effect on chaos in foreign exchange markets. As one of the main economic structures in the globalization process, competition between two target exchange rates with the same base currency forms a simple competitive exchange rate relation, where each exchange rate follows the chaotic model of De Grauwe (Exchange Rate Theory-Chaotic Models of Foreign Exchange Markets, Blackwell, Oxford, Cambridge, MA, 1993). The main discovery is, while each exchange rate is in its non-chaotic parameter regions, the effect of competition will “hatch” butterfly-like chaotic attractors in the competitive market. The positive Lyapunov exponent in the market explains the reason why chaos occurs. [Copyright &y& Elsevier]

We present a new two phase model of economic production processes which is a non-linear dynamical version of von Neumann''s neoclassical model of production, including a market price-setting phase as well as a production phase. The rate of an economic production process is observed, for the first time, to depend on the minimum of its input supplies. This creates highly non-linear supply and demand dynamics. By numerical simulation, production networks are shown to become unstable when the ratio of different products to total processes increases. This provides some insight into observed stability of competitive capitalist economies in comparison to monopolistic economies. Capitalist economies are also shown to have low unemployment. [Copyright &y& Elsevier]

In the coming decades, climate change is projected to cause carbon dioxide fertilization effects in pine forests in the US Southeast. Resulting changes in pine (loblolly) growth will impact forest markets and regional carbon sequestration. We examine this impact in the context of baseline demand scenarios of increasing sophistication to determine the relative impact of growth and business as usual assumptions on forest growing stock volume, removals, prices and carbon sequestration. We use above-ground biomass data generated from the 3-PG forest growth model based on 20 climate models and Representative Concentration Pathway scenarios 4.5 and 8.5. We examine forest market and carbon sequestration impacts using the Sub-Regional Timber Supply model, with and without climate change-related growth. Results suggest that forest growing stock will increase under all climate change scenarios. Timber prices under carbon fertilization are projected to be lower over the long run. [ABSTRACT FROM AUTHOR]

Abstract: This work examines the impact that economic growth can have on biodiversity and on the ecological dynamics that would naturally emerge in the absence of human activity. The loss of biodiversity may induce policy makers to implement defensive actions that prevent single species from extinction. These defensive actions, however, may deeply alter the natural dynamics of interaction between species, leading to an ecological equilibrium that is completely different from the one that would exist in the absence of human intervention. This suggests that there might exist a conflict between preserving biodiversity (through stabilization of the ecological system) and preserving the intrinsic features of the ecological dynamics. [Copyright &y& Elsevier]