Defining viable recovery paths toward sustainable fisheries

This paper develops a formal analysis of the recovery process for a fishery, from crisis situations to desired levels of sustainable exploitation, using the theoretical framework of viable control. We define sustainability as a combination of biological, economic and social constraints which need to be met for a viable fishery to exist. Biological constraints are based on the definition of a minimum resource stock to be preserved. Economic constraints relate to the existence of a guaranteed profit per vessel. Social constraints refer to the maintenance of a minimum size of the fleet, and to the maximum speed at which fleet adjustment can take place. Using fleet size adjustment and fishing effort per vessel as control variables, we first identify the states of this bioeconomic system for which sustainable exploitation is possible, i.e. for which all constraints can be dynamically met. Such favorable states are called viable states. We then examine possible transition phases, from non-viable to viable states. We characterize recovery paths with respect to the time of crisis of the trajectory, which is the number of periods during which the constraints are not respected. The approach is applied to the single stock of the bay of Biscay Nephrops fishery. The transition path identified through the viability approach is compared to the historical recovery process, and to both open-access and optimal harvesting scenarios.     

Regulation of the evolution of the architecture of a network by tensors operating on coalitions of actors

Socio-economic networks, neural networks and genetic networks describe collective phenomena through constraints relating actions of several actors, coalitions of these actors and multilinear connectionist operators acting on the set of actions of each coalition. We provide a class of control systems governing the evolution of actions, coalitions and multilinear connectionist operators under which the architecture of the network remains viable. The controls are the “viability multipliers” of the “resource space” in which the constraints are defined. They are involved as “tensor products” of the actions of the coalitions and the viability multiplier, allowing us to encapsulate in this dynamical and multilinear framework the concept of Hebbian learning rules in neural networks in the form of “multi-Hebbian” dynamics in the evolution of connectionist operators. They are also involved in the evolution of coalitions through the “cost” of the constraints under the viability multiplier regarded as a price.     

A viability analysis for a bio-economic model

This paper presents a simple dynamic model dealing with the management of a marine renewable resource. But instead of studying the ecological and economic interactions in terms of equilibrium or optimal control, we pay much attention to the viability of the system or, in a symmetric way, to crisis situations. These viability/crisis situations are defined by a set of economic and biological state constraints. The analytical study focuses on the compatibility between the state constraints and the controlled dynamics. Using the mathematical concept of viability kernel, we reveal the situations and, if possible, management options to guarantee a perennial system. Going further, we define ‘overexploitation’ indicators by the time of crisis function. In particular, we point out irreversible overexploitation configurations related to the resource extinction.     

自生能力、经济转型与新古典经济学的反思

现有的新古典经济学理论体系把企业具有自生能力作为暗含的前提。但是 ,转型中国家和其他许多发展中国家的企业却因政府的赶超愿望 ,进入不具比较优势的产业而不具自生能力。当经济中大量企业缺乏自生能力时 ,实行根据新古典经济学所制定的改革或转型政策 ,往往达不到预期效果 ,而且 ,可能给社会带来巨大痛苦。本文主张 ,在分析社会主义经济、转型经济和发展经济问题时 ,放弃现有的新古典经济学体系中企业具有自生能力的暗含前提 ,把企业是否具有自生能力作为一个具体的考虑变量 ,这是新古典经济学理论的必要发展。     

Entrepreneurship in post‐conflict transition1

We examine new self‐employment entry and its viability in Bosnia and Herzegovina, using a rich household survey for the years 2001–2004. We find that wealthier households are more likely to engage in viable self‐employment and create employment suggesting an important role for financing constraints. Specifically, although having an existing bank relationship is not significantly related to the entry decision, it is positively related to the survival for new entrepreneurs and their employment creation. We also find a non‐linear relationship between remittances and entry in that individuals not receiving remittances are more likely to enter self‐employment; but, if they do receive them, the likelihood of starting a business increases in the fraction of wealth received from domestic remittances. Finally, people working in the informal sector are more likely to become viable entrepreneurs, particularly those provided with loans from micro‐credit organizations. These findings support the perception of the informal sector as an incubator for formal self‐employment in the early years of transition.     

Policy assessment and simulation of actor orientation for sustainable development

Understanding, assessing, and simulating behavior requires knowledge of the precepts that are explicitly or implicitly orienting behavior. Human actors can be viewed as (conscious) self-organizing systems attempting to remain viable in a diverse environment containing other self-organizing systems (other human actors, organisms, ecosystems, etc.), all driven by their own viability (sustainability) interests. These fundamental system interests, or basic orientors, have emerged in response to general environmental properties and are therefore identical across self-organizing systems: existence, effectiveness, freedom of action, security, adaptability, coexistence. Even in simulated actors learning to ‘survive’ in a difficult environment, the basic orientors emerge in the (simulated) evolutionary process — but different actors may evolve into different ‘cultural types’ with different orientor emphasis. Since balanced attention to all basic orientors is crucial for viability, the set of orientors can be used to derive indicators that facilitate comprehensive viability and sustainability assessments. The paper outlines the theoretical approach of ‘orientation theory’ and its application to the assessment and simulation of sustainable development issues. The formal approach of mapping indicators on basic orientors and assessing sustainability dynamics is illustrated using Worldwatch indicator time series. In an actor simulation this approach is used to successfully guide a small global model onto a sustainable path with high ‘quality of life’.     

Sustainability of an economy with an exhaustible resource: A viable control approach

We examine the conditions for the sustainability of a production–consumption system based on the use of an exhaustible natural resource. Instead of studying the environmental and economic interactions in terms of optimal control, we focus on the viability of the system, defined by a set of constraints combining guaranteed consumption and a stock of resources to be preserved at all times, which refers to a Rawlsian intergenerational equity perspective. Using the mathematical concept of viability kernel, which makes it possible to deal with the consistency between constraints and controlled dynamics, we exhibit the sustainable technological configurations and, whenever possible, the policy options and environmental-economic states required to obtain a perennial system. We point out the flexibility of the sustainable “extraction–consumption” choices and we show how they are neither reduced to constant consumption paths nor to Hartwick’s rule. Numerical simulations illustrate the general results.     

Innovation and Competition: The Role of Finance Constraints in a Duopoly Case

In this paper we analyse the role of financial resources in a process of competition interpreted as a continuous restructuring of productive capacities. Financial constraints appear an essential means of co-ordination. Co-ordination with the environment where this process of restructuring takes place for the process itself to be viable and co-ordination between firms for the survival of competition.     

送转行为、年报绩效信息与融资约束

基于我国上市公司数据,运用实证研究方法发现,送转行为是上市公司信息传递的有效机制,它有助于缓解我国上市公司由于管理者与其他利益相关者之间的信息不对称所造成的公司融资约束问题,特别是对于那些上年年报财务绩效不十分理想的受融资约束的公司,送转行为对缓解融资约束效果更为突出。我国上市公司的送转行为并非完全出于对市场投资者的迎合,而是一种有效的信号传递方式。在运用Heckman两步法控制了样本自选择问题之后,文章所得研究结论仍然成立。     

Technology,property rights and organizational diversity in the software industry

Why do open- and closed-source productions co-exist? To address this question, the paper studies the viability of distinct systems for software development. The model shows that: (a) for low design costs of modularity, both open- and closed-source productions are viable systems; (b) closed-source production is more likely to be adopted the greater the expected rents on software; and (c) production efficiency is not a necessary condition for the stochastic stability of a system to obtain. These three results can shed light on the emergence of organizational diversity in the software industry. The paper adds to the literature in three ways: first, it considers property rights and technology as endogenous variables in the process of system design; second it argues that in producing software multiple equilibrium designs may exist; and third, it shows that, in because of high rents and low design costs of modularity, production inefficiency can be persistent.     

Viable Ramsey economies

The Ramsey model of economic growth is revisited from the perspective of viability theory. The Ramsey model, augmented with minimal consumption and sustainability criteria, becomes a viability problem. The framework allows for a clear picture of optimal viable, optimal non‐viable, and viable non‐optimal paths. The drastic sacrifices in terms of present consumption required by the implementation of Brundtland sustainability are visualized, the rich countries bearing the major part of the burden. The econometric analysis of viability sets enhances the role of technological progress in ensuring Brundtland sustainability. Preference parameters such as the pure time preference rate are statistically non‐significant.     

Fishery externalities and biodiversity: Trade-offs between the viability of shrimp trawling and the conservation of Frigatebirds in French Guiana

Sustainable management of natural resources, and in particular fisheries, must take into account several conflicting objectives. This is the case in the French Guiana shrimp fishery for which profitability objectives imply a reduction in the fishing activity. On the one hand, this fishery has negative externalities on marine biodiversity due to discards. On the other hand, this fishery has positive externalities on the economy of the local community and interestingly enough on a protected seabird species in the area (the Frigatebird that feeds on discards). In this paper, we examine the viability of that system considering two sustainability objectives: an economic objective in terms of the profitability of the fishing activity, and a conservation objective in terms of the Frigatebird population. For that purpose, we have developed a dynamic model of that bioeconomic system and study here the trade-offs between the two conflicting objectives. It provides a means to quantify the necessary give and takes involving the economic and ecological objectives that would ensure a viable management solution. Our study confirms the relevance of the viability approach to address natural resource management issues, which should lead to the development of new tools for the arbitration of conflicting sustainability objectives. In particular, such tools could be used as a quantitative basis for cost–benefit analysis taking into account environmental externalities.     

Fishery externalities and biodiversity: Trade-offs between the viability of shrimp trawling and the conservation of Frigatebirds in French Guiana

Sustainable management of natural resources, and in particular fisheries, must take into account several conflicting objectives. This is the case in the French Guiana shrimp fishery for which profitability objectives imply a reduction in the fishing activity. On the one hand, this fishery has negative externalities on marine biodiversity due to discards. On the other hand, this fishery has positive externalities on the economy of the local community and interestingly enough on a protected seabird species in the area (the Frigatebird that feeds on discards). In this paper, we examine the viability of that system considering two sustainability objectives: an economic objective in terms of the profitability of the fishing activity, and a conservation objective in terms of the Frigatebird population. For that purpose, we have developed a dynamic model of that bioeconomic system and study here the trade-offs between the two conflicting objectives. It provides a means to quantify the necessary give and takes involving the economic and ecological objectives that would ensure a viable management solution. Our study confirms the relevance of the viability approach to address natural resource management issues, which should lead to the development of new tools for the arbitration of conflicting sustainability objectives. In particular, such tools could be used as a quantitative basis for cost–benefit analysis taking into account environmental externalities.     

Socialism,Spillovers and Markets in Cuba

This article undertakes an empirical evaluation of Cuba's new development strategy placing tourism at the heart of the process of incorporating markets into a socialist system. The principal research question is whether the introduction of markets related to the Cuban tourism complex has been as successful in establishing viable backward linkages to industry as claimed. Drawing on a multitude of quantitative and qualitative sources, the article demonstrates that backward linkage building has been quite successful and even made possible a transformation of Cuba's formerly so dependent trade structures. However, there are signs that backward linkages are not as viable as could be desired. Other complementary reforms beside the introduction of markets are necessary, such as fighting soft budget constraints in user and producer firms. The article concludes that it will be difficult to fight the roots of the inherited incentive problem without initiating fundamental labour market reforms.     

Education and growth with endogenous debt constraints

When future human capital cannot be alienated, households are allowed to borrow up to the point where it is in their own interest not to default. In such a framework, endogenous borrowing limits arise as the outcome of individual rationality constraint. In a model where education is the engine of growth, we show that endogenous borrowing constraints imply global indeterminacy. Comparing outcomes across the various equilibria we show that the relation between growth and yields is hump-shaped. Maximum growth can arise in an equilibrium with binding borrowing constraints, specially if the elasticity of human capital to education spending is large. Deepening financial markets promotes long-run growth in the case of a poverty trap, but not necessarily otherwise. On the methodological side, our approach stresses the importance of studying borrowing limits in general equilibrium, not only in small open economies. Philippe Michel passed away on July 22, 2004. His death is a great loss for his friends and for the overlapping generations and optimal control community.     

Evaluating the impact of inequality constraints and parameter uncertainty on optimal portfolio choice

We present new analytical results for the impact of portfolio weight constraints on an investor’s optimal portfolio when parameter uncertainty is taken into account. While it is well known that parameter uncertainty and imposing weight constraints results in reduced certainty equivalent returns, in the general case, there are no analytical results. In a special case, commonly used in the funds management literature, we derive analytical expression for the certainty equivalent loss that does not depend on the risk aversion parameter. We illustrate our theoretical results using hedge fund data, from the perspective of a fund-of-fund manager. Our contribution is to formalize the framework to investigate this problem, as well as providing tractable analytical solutions that can be implemented using either simulated or asset manager returns.     

Is Regionalism Viable? A Case for Global Free Trade

We assume an imperfectly competitive world with n commodities and address the question of whether or not (regional) trade blocs are viable. To answer this fundamental question, we use a notion of stability, offered by Greenberg (1990) , and show that regional trade blocs are not viable as they are not stable. On the other hand, we demonstrate that a global trade bloc is viable. Therefore, our results provide theoretical support for advocates of global free trade.     

Bioeconomic modeling for control of weeds in natural environments

When a weed invasion is first discovered a decision has to be made on whether to attempt to eradicate it, contain it or do nothing. Ideally, these decisions should be based on a complete benefit-cost analysis, but this is often not possible. A partial analysis, combining knowledge of the rate of spread, seedbank longevity, costs of control and techniques of economic analysis, can assist in making a good decision. This paper presents a decision model to determine when immediate eradication of a weed should be attempted, or more generally whether weed control should be attempted at all. The technique is based on identifying two ‘switching points’: the invasion size at which it is no longer optimal to attempt eradication but where containment may be an option; and the invasion size at which it becomes optimal to apply no form of control at all. The model is applied to a woody perennial weed in a natural environment. The results show that seedbank longevity is the main constraint on the maximum eradicable area and spread rate is the main constraint on the maximum containment area. Stochastic simulations are undertaken to derive probability distributions of costs which are than used to evaluate the effect of budget constraints on areas that can be eradicated. We find that, in the absence of a budget constraint, it may be desirable to eradicate invasions from areas as large as 8000 ha, but when budget constraints typical of those faced by agencies in Australia are introduced, feasible eradicable areas are less than 1000 ha.     

Fiscal Discipline and Exchange Rate Systems

A new 'fiscal' theory of price determination has implications for exchange rate systems and common currency areas. We show that deeper monetary integration requires the discipline of a Ricardian regime ; that is, the government must guarantee fiscal solvency for any sequence of prices or exchange rates. Particularly striking results are that a currency peg is not credible without the discipline of a Ricardian regime, and a common currency area is not viable if fiscal policy in two (or more) of the countries in the union is Non-Ricardian. Interestingly, constraints written into the Maastricht Treaty are sufficient for a Ricardian regime.     

Groundwater Management in a Food Security Context

This article analyzes the sustainability of market-based instruments such as tradable permits for the management of a renewable aquifer used for irrigated agriculture. In our dynamic hydro-economic model, a water agency aims at satisfying a food security constraint within a tradable permit scheme in the presence of myopic heterogeneous agents. We identify analytically the viability kernel that defines the states of the resource yielding inter-temporal feasible paths able to satisfy the set of constraints over time and the associated set of viable quota policies. We then illustrate the theoretical results of the paper with numerical simulations based on the Western La Mancha aquifer.