A step beside the maximin path: Can we sustain the economy by following Hartwick's investment rule?

If sustainability is interpreted as the requirement to sustain consumption or utility at an optimal level, a maximin objective appears to be relevant. The sustained economy is characterized by an optimal investment following Hartwick's investment rule. This paper examines how the sustainability of a production-consumption economy with a non-renewable resource is modified in the neighborhood of the maximin path, i.e. when the consumption and the resource price are not optimal. A Sustainable Consumption Indicator is introduced in order to characterize the sustainability of constant consumption paths, defined as deviations from the maximin path. We describe how an over-consumption jeopardizes future sustainability.     

Groundwater management under heterogeneous land tenure arrangements

We develop a groundwater extraction model that considers the Marshallian inefficiency associated with sharecropping and use data from Pakistan to simulate the impact of an open access regime and of optimal management on groundwater extractions, the state of the aquifer, and annual net benefits through time. We also evaluate a price instrument as a mechanism of inducing optimal extractions. Under both open access and optimal management, we observe notable differences in groundwater extractions and the water table level between the tenure model (which considers the behavior of both owner cultivators and sharecroppers) and the baseline model (which includes the behavior of only owner cultivators). We also find a modest difference in the aggregate net benefits generated by the two models. The results offer new insights—vis-à-vis land tenure heterogeneity—into the evaluation of more effective policies for groundwater management and aquifer sustainability.     

Ecological-economic viability as a criterion of strong sustainability under uncertainty

Strong sustainability, according to the common definition, requires that different natural and economic capital stocks be maintained as physical quantities separately. Yet, in a world of uncertainty this cannot be guaranteed. To therefore define strong sustainability under uncertainty in an operational manner we propose to use the concept of viability. Viability means that the different components and functions of a dynamic, stochastic system at any time remain in a domain where the future existence of these components and functions is guaranteed with sufficiently high probability. We develop a unifying and general ecological-economic concept of viability that encompasses the traditional ecological and economic notions of viability as special cases. It provides an operational criterion of strong sustainability under a mild form of uncertainty and for medium spatial and temporal scales. We illustrate this concept and demonstrate its usefulness by applying it to livestock grazing management in semi-arid rangelands.     

Uncertainty and sustainability in the management of rangelands

We analyze a dynamic and stochastic ecological-economic model of grazing management in semi-arid rangelands. The ecosystem is driven by stochastic precipitation. A risk averse farmer chooses a grazing management strategy under uncertainty such as to maximize expected utility from farming income. Grazing management strategies are rules about which share of the rangeland is given rest depending on the actual rainfall in that year. In a first step we determine a myopic farmer's optimal grazing management strategy and show that a risk averse farmer chooses a strategy such as to obtain insurance from the ecosystem: the optimal strategy reduces income variability, but yields less mean income than possible. In a second step we analyze the long-run ecological and economic impact of different strategies. We conclude that a myopic farmer, if he is sufficiently risk averse, will choose a sustainable grazing management strategy, even if he does not take into account long-term ecological and economic benefits of conservative strategies.     

Insurance,credit, and technology adoption: Field experimental evidencefrom Malawi

Does production risk suppress the demand for credit? We implemented a randomized field experiment to ask whether provision of insurance against a major source of production risk induces farmers to take out loans to adopt a new crop technology. The study sample was composed of roughly 800 maize and groundnut farmers in Malawi, where by far the dominant source of production risk is the level of rainfall. We randomly selected half of the farmers to be offered credit to purchase high-yielding hybrid maize and groundnut seeds for planting in the November 2006 crop season. The other half of farmers were offered a similar credit package, but were also required to purchase (at actuarially fair rates) a weather insurance policy that partially or fully forgave the loan in the event of poor rainfall. Surprisingly, take-up was lower by 13 percentage points among farmers offered insurance with the loan. Take-up was 33.0% for farmers who were offered the uninsured loan. There is suggestive evidence that reduced take-up of the insured loan was due to farmers already having implicit insurance from the limited liability clause in the loan contract: insured loan take-up was positively correlated with farmer education, income, and wealth, which may proxy for the individual's default costs. By contrast, take-up of the uninsured loan was uncorrelated with these farmer characteristics.     

Well-being and/or quality of life in EU countries through a multidimensional index of sustainability

The aim of my paper is to demonstrate that Sen's theory of well-being can be applied to make the concept of sustainable human development operational through the building of a multidimensional index of sustainability which takes into account, at the same time, economic, social and environmental variables. This index may be considered an alternative to the current measures of welfare/sustainability since not only conventional measures such as GDP, but also multi-attribute indices, such as Human Development Index (HDI), Genuine Savings, Index of Sustainable Economic Welfare (ISEW) etc., are found to be inadequate to make the concept of sustainable development operational. Therefore, the limitations of these measures of welfare/sustainability justify the search for a new index of sustainability. This index will show, at the operational level, how Sen's theory of well-being can be useful to sustainable development. It was applied to EU countries using the standardised deviation methodology being the closest and most suitable methodology to be adopted for building multidimensional indices. The factor analysis methodology will also be used in my paper. Lastly, the comparison between Sen's trend of sustainability and GDP trend index number-which are both of them applied to Italy-will show how much the criticisms and the limitations directed towards the indicator of GDP are founded.     

Management of an annual fishery in the presence of ecological stress: The case of shrimp and hypoxia

The emergence of ecosystem-based management suggests that traditional fisheries management and protection of environmental quality are increasingly interrelated. Fishery managers, however, have limited control over most sources of marine and estuarine pollution and at best can only adapt to environmental conditions. We develop a bioeconomic model of optimal harvest of an annual species that is subject to an environmental disturbance. We parameterize the model to analyze the effect of hypoxia (low dissolved oxygen) on the optimal harvest path of brown shrimp, a commercially important species that is fished in hypoxic waters in the Gulf of Mexico and in estuaries in the southeastern United States. We find that hypoxia alters the qualitative pattern of optimal harvest and shifts the season opening earlier in the year; more severe hypoxia leads to even earlier season openings. Failure to adapt to hypoxia leads to greater losses when the effects of hypoxia are more severe. However, rent gains from adapting fishery management to hypoxia are relatively small compared to rent losses from the hypoxia effect itself. This suggests that it is critical for other regulatory agencies to control estuarine pollution, and fishery managers need to generate value from the fishery resources through other means such as rationalization.     

The impact of culture and ecology on cooperation in a common-pool resource experiment

Context affects decision-making in many ways. In this paper we explore differences in cooperation behaviour between communal farmers in Namibia and South Africa, who share the same ethnic origin but have had different historical and ecological constraints. We report on a series of field experiments based on a common-pool resource model. Our experimental design is framed according to the grazing situation in semi-arid rangelands. Dependent on the behaviour in previous rounds, participants are facing different states of resource availability with varying need to cooperate, coordinate and to be patient. While only 4% of the grazing areas in South Africa remain in good quality, Namibians achieve a level of 42%. We analyse the different experimental states and find that Namibians behave in all states more cooperatively. We argue that the large difference between the two regions is due to a combination of different historical developments and ecological preconditions: Namibian resource users have a longer experience in cooperative resource management and intact traditional norms. Moreover, the real-life payoffs to cooperation are higher in Namibia stemming from ecological factors.     

汽车保险发展历程与现状浅析

近年来中国汽车产业发展迅速,汽车消费的增长必将带动汽车保险业迅速发展,特别是按照入世协议我国将逐步开放保险市场,中国汽车保险业将面临严峻的挑战,如何应对这一挑战,成为我国汽车保险业不容忽视的问题。本文试图通过分析世界汽车保险业的发展历程与现状的分析,将为中国汽车保险业提供借鉴。     

Priority Network Access Pricing for Electric Power

We propose a priority-pricing scheme for zonal access to the electric power grid that is uniform across all buses in a zone. The independent system operator (ISO) charges bulk power traders a per unit ex ante transmission access fee. The zonal access fee serves as an access insurance premium that entitles a bulk power trader to either physical injection of one unit of energy or a compensation payment. The access fee per MWh depends on the injection zone and a self-selected strike price that serves as an insurance deductible that determines the scheduling priority of the insured transaction and the compensation level in case of curtailment. Inter-zonal transactions are charged (or credited) with an additional ex post congestion fee equal to the differences in zonal spot prices. The compensation for curtailed transactions equals the difference between the realized zonal spot price and the selected strike price (deductible level). The ISO manages congestion so as to minimize net compensation payments and thus, curtailment probabilities increase with strike price and for any particular strike price may vary from bus to bus. We calculate the rational expectations equilibrium for three-, four- and six-node systems and demonstrate that the efficiency losses of the proposed second best scheme relative to the efficient dispatch solutions are modest.     

The economic growth impact of natural disasters in developing countries: Evidence from hurricane strikes in the Central American and Caribbean regions

In this paper we investigate the macroeconomic impact of natural disasters in developing countries by examining hurricane strikes in the Central American and Caribbean regions. Our innovation in this regard is to employ a wind field model on hurricane track data to arrive at a more scientifically based index of potential local destruction. This index allows us to identify damages at a detailed geographical level, compare hurricanes' destructiveness, as well as identify the countries that are most affected, without having to rely on potentially questionable monetary loss estimates. Combining our destruction index with macroeconomic data we show that the average hurricane strike caused output to fall by at least 0.83 percentage points in the region, although this depends on controlling for local economic characteristics of the country affected and what time of the year the storm strikes.     

扩大中国农业保险有效需求的对策研究

农业保险是农民转移农业风险的重要手段。农民人均收入过低、农业土地分散经营、保险费率过高、农业风险管理手段多样化和农民保险意识淡薄等是影响农业保险有效需求的重要因素,为此应采取提高中国农业用地集中程度、切实提高农民收入水平、开发农业保险新险种、提高对农业保险的宣传力度以及政府加大对农业保险支持力度等相应对策。     

Sustainable management of extensively managed savanna rangelands

Classic rangeland theory advocates stocking rangelands at relatively low and constant levels. This theory has been labelled inappropriate for savanna rangelands, because savannas are strongly influenced by stochastic processes. Opportunistic strategies that force animal numbers to track available forage have been proposed as an alternative management paradigm. However, no studies have examined whether these opportunistic strategies are sustainable or optimal. We developed a simulation model of a savanna rangeland to identify optimal, sustainable strategies for the management of extensive rangelands. We optimised the utility of agents who are motivated by economic, production or ecological factors under both deterministic and stochastic conditions. In all cases we found that it was optimal to manage the system conservatively and not opportunistically. Moreover, it was optimal to manage more conservatively under stochastic conditions. Key elements of the conservative strategy were to stock at low levels and to use fire to control tree abundance and thereby maintain the system in a grass dominated state. We conclude that opportunistic strategies of range management although intuitively appealing are not optimal.     

Consumption risk, technology adoption and poverty traps: Evidence from Ethiopia

Much has been written on the determinants of technology adoption in agriculture, with issues such as input availability, knowledge and education, risk preferences, profitability, and credit constraints receiving much attention. This paper focuses on a factor that has been less well documented: the differential ability of households to take on risky production technologies for fear of the welfare consequences if shocks result in poor harvests. Building on an explicit model, this is explored in panel data from Ethiopia. Historical rainfall distributions are used to identify consumption risk. Controlling for unobserved household and time-varying village characteristics, it emerges that not just ex ante credit constraints, but also the possibly low consumption outcomes when harvests fail, discourage the application of fertilizer. The lack of insurance or alternative means of keeping consumption smooth leaves some trapped in low return, lower risk agriculture, one of the mechanisms through which poverty perpetuates itself in agrarian settings.     

Modeling national flood insurance policy holding at the county scale in Florida, 1999-2005

We analyze household flood insurance purchases in Florida from 1999 to 2005, and the extent to which household insurance purchases correspond with flood mitigation activities by local governments involved in the Federal Emergency Management Agency's (FEMA) Community Rating System (CRS). Regression results indicate that household flood insurance purchases correlate strongly with local government mitigation activities, adjusting for hazard experience, hazard proximity, and community demography. Policy implications of this observed relationship are discussed, assuming four temporal order and floodplain development scenarios, with particular attention to the congruence of outcomes relative to policy objectives.     

Income-contingent loan with personal insurance policy: an empirical assessment using Spanish data

We propose an Income Contingent Loan that defers the payment of university fees and charges a fixed proportion of gross income for 30 years or until the debt is written off. Under these conditions, some participants in the scheme will have insufficient income to fully repay their loan balances. The deficit will be covered by the taxpayer, who ultimately bears the risk of investing in higher education. We then propose to transfer this risk to the student by adding a mandatory personal insurance policy to the individual loan. We calculate the premium required for the system to break even in Spain when everybody pays the insurance cost. Alternatively, the payment of the premium can be deferred, adding it to total debt. Then, some participants in the scheme will have insufficient income to even pay the insurance cost, and the premium needs to be increased to maintain the sustainability of the program. Although these mechanisms imply redistribution towards borrowers who end up being low earners, we show that middle-income individuals contribute a higher proportion of their incomes to covering for those unable to repay. To provide the system with more internal progressivity, we propose to impose a minimum period of repayment.     

Quantifying production-environment tradeoffs for grazing land management — A case example from the Australian rangelands

Contemporary management of Australian rangeland grazing enterprises is characterised by concurrent processes of a continuing intensification of land management practices and simplification of landscape ecological processes. This dual characteristic is associated with increasing levels of potential conflict between land management practices that promote improved economic performance of these enterprises at the apparent expense of the ecological health of the landscape; and vice versa. A framework is described for assisting private range managers to make an assessment of prospective production and environmental tradeoffs for a range of rangeland management practices. Two examples of the application of the framework are presented - tree clearing and riparian fencing - both using case studies of rangeland livestock enterprises that are located in two regions of the northern Australian rangelands.     

The cost of natural capital consumption: Accounting for a sustainable world economy

The System for integrated Environmental and Economic Accounting (SEEA) has been criticized in this journal for ignoring the benefits of ecosystem services for human well-being. This paper argues that extended national accounts should not attempt measuring economic welfare. Rather, they could and should assess the environmental sustainability of economic activity as the cost of natural capital consumption. The global application of SEEA concepts and methods demonstrates the feasibility of international green accounting. For the world economy, sustainability costs run to about 3 trillion US$ or 6% of world GDP. Large variations at national and regional levels suggest that conventional economic indicators may significantly overstate economic progress in some parts of the world. Data gaps and lack of data comparability affect these first estimates. National and international statistical services should be more aggressive in greening the national accounts. More prudent and more sustainable economic policies might be the result.     

Unsustainable timber harvesting, deforestation and the role of certification

Deforestation is a major environmental issue, while demand for timber products increases rapidly in the developing world. One can thus wonder whether forest harvesting is sustainable worldwide, or if demand for timber products is fulfilled with the products from deforestation. Our panel data analysis shows that countries where timber harvesting is more important tend to experience larger deforestation rates than others, giving the intuition that forest harvesting is generally not sustainable. We also show that timber certification is negatively related to deforestation and thus seems to be a good indicator of harvesting sustainability.