portfolio resampling review and critique a well understood fact of asset allocation is that the traditional portfolio optimization algorithm is too powerful for the quality of the inputs recently a new concept called resampled efficiency has been introduced into the asset management world to deal with estimation error the objective of this article is to describe this new technology put it into the context of established procedures and point to some peculiarities of the approach even though portfolio resampling is a thoughtful heuristic some features make it difficult to interpret by the inexperienced portfolio resampling review and critique a comment

the price of pollution a dual approach to valuing so2 allowances under the 1990 clean air act amendments a market based scheme to reduce u s sulfur dioxide emissions takes effect in 1995 indications are that participation in the market will be light and allowance prices will be lower than was once expected using an output distance function approach for wisconsin coal burning utility plants we estimate the shadow price of so2abatement which should approximate the allowance price the estimated average shadow price is above the prices at which the few observed allowance trades have occurred wisconsin s stringent state so2legislation may explain a portion of this divergence

a general mean variance approximation to expected utility for short holding periods the mean variance model is precisely consistent with the expected utility hypothesis only in the special cases of normally distributed security returns or quadratic utility functions there is little evidence however that security returns follow normal distributions see 13 for references and quadratic preferences can be shown to generate implausible results exhibiting increasing absolute risk aversion in the pratt ll arrow 1 2 sense and displaying negative marginal utility after some finite wealth level in addition hakansson 4 has shown that single period mean variance efficient portfolios can have disastrous consequences over time even when return distributions are stationary such criticisms of the mean variance approach within the von neumann morgenstern framework have prompted several writers to suggest that investors maximize the expected value of utility functions with more realistic properties while others have criticized the single period focus of the model one popular alternative utility function is the logarithmic function which exhibits decreasing absolute risk aversion and conveniently leads to myopic decision processes through time i e investors treat each period as if it were the last basing investment decisions on that period s wealth and return distributions only 8 4 other utility functions with constant relative risk aversion such as the power function also imply myopic decision rules within a multiperiod setting

the north american horticultural industry and the risk of plant invasion we develop a monopolistic competition model of the horticultural industry and estimate the resulting profit function with u s and canadian industry data combining the results with a hazard analysis of the characteristics of exotic plants introduced in north america we explore optimal tax simulations for internalizing the risk and costs of a potential plant invasion if the share of the exotic plant sales in final profits is large then the resulting annual fee will be high discouraging the expansion of the nursery industry however the annual revenues could fund efforts to mitigate the damages resulting from any accidental plant invasion

substitutability among undesirable outputs in recent years economists have started to move beyond calculating regulatory effects on a pollutant by pollutant basis since their interaction is important in this study we take up this issue to allow for joint production of multiple pollutants and marketable output we specify our technology using a directional distance function this allows us to treat pollutants as joint outputs yet accounts for their undesirability we estimate the distance function for a sample of coal fired electric power plants from 1985 to 1998 which includes the first 4 years of phase i of the clean air act amendments of 1990 we focus on the interaction between so2 and no x as they became more highly regulated and estimate shadow prices of the pollutants and the morishima elasticity of transformation between two pollutants no x and so2 as well as with respect to the desirable output kilowatt hours of electricity as expected we find that power plants increase no x emissions as they decrease so2 i e they are subs

protectionism trade and measures of damage from exotic species introductions unintentional introductions of nonindigenous plants animals and microbes cause significant ecological and agricultural crop damage worldwide trade in both manufactured and agricultural goods is a primary vector for such introductions fusing simple models of trade and biological introductions we explore the links between trade protectionism and damage arising from exotic species introductions we show that it is possible for freer trade to reduce damage arising from exotic species invasions we also show how current measures of damage heavily weighted toward agricultural damage serve as misleading indicators of how restrictions to trade affect total losses arising from exotic species

application of portfolio theory to asset based biosecurity decision analysis abstract a key challenge for biosecurity decision making is how best to allocate scarce resources across multiple environmental assets the allocation of funds for the best return from investment requires a careful assessment of expected return and uncertainty in this paper we applied a portfolio theory based decision support tool that helps determine resource allocation in a way that maximizes expected return and minimizes uncertainty our framework offers three advancements to the literature first it helps in making resource allocation decisions across multiple pests that affect multiple environmental assets second it incorporates multiple sources of uncertainty in the decision analysis including economic value uncertainty finally it demonstrates a generic approach to design a choice experiment study to estimate monetary values of a broad group of environmental assets we find that a portfolio based framework applied in conjunction with a choice experiment study can be a useful tool to guide biosecurity resource allocation decisions our results show that disregarding value uncertainty may cause bias by underestimating true uncertainty in the opportunity set the choice experiment study revealed substantial positive non market values generated by environmental biosecurity in australia however significant preference heterogeneity across respondents with regards to different biosecurity outcomes was observed

efficiency analysis of chinese industry a directional distance function approach two efficiency measures of chinese industry were estimated at the provincial level from 1994 to 2002 using a directional output distance function one is a traditional efficiency measure that considers only desirable output while the other considers both desirable and undesirable outputs simultaneously a comparison of the two measures revealed that efficiency levels are biased only if desirable output is considered five coastal provinces municipalities that have attracted a large amount of foreign direct investment are found to be the most efficient when only desirable output is considered and also when both desirable and undesirable outputs are considered however omitting undesirable output tends to lead to an overestimate of industrial efficiency levels in shandong sichuan and hebei provinces we also found that a province s industrial structure has significant effects on its efficiency levels

some models for estimating technical and scale inefficiencies in data envelopment analysis in management contexts mathematical programming is usually used to evaluate a collection of possible alternative courses of action en route to selecting one which is best in this capacity mathematical programming serves as a planning aid to management data envelopment analysis reverses this role and employs mathematical programming to obtain ex post facto evaluations of the relative efficiency of management accomplishments however they may have been planned or executed mathematical programming is thereby extended for use as a tool for control and evaluation of past accomplishments as well as a tool to aid in planning future activities the ccr ratio form introduced by charnes cooper and rhodes as part of their data envelopment analysis approach comprehends both technical and scale inefficiencies via the optimal value of the ratio form as obtained directly from the data without requiring a priori specification of weights and or explicit delineation of assumed functional forms of relations between inputs and outputs a separation into technical and scale efficiencies is accomplished by the methods developed in this paper without altering the latter conditions for use of dea directly on observational data technical inefficiencies are identified with failures to achieve best possible output levels and or usage of excessive amounts of inputs methods for identifying and correcting the magnitudes of these inefficiencies as supplied in prior work are illustrated in the present paper a new separate variable is introduced which makes it possible to determine whether operations were conducted in regions of increasing constant or decreasing returns to scale in multiple input and multiple output situations the results are discussed and related not only to classical single output economics but also to more modern versions of economics which are identified with contestable market theories

technical efficiency shadow price and substitutability of chinese industrial so2 emissions a parametric approach abstract in china s transition process towards sustainable development fighting against the rising so2 emission has become a great and urgent challenge based on a parametric quadratic directional distance function this paper investigates the inefficiency level shadow price and substitution elasticity of chinese industrial so2 emission from 1998 to 2011 the results show a u shape for the technical inefficiency indicating an efficiency improvement before 2005 but it getting worse since then which is that the east area displays a declining trend while the west goes up and the middle follows the national pattern at the east middle west region level as of the shadow price and morishima elasticity both the national and regional levels hold an increasing trajectory the shadow price is continuously increased a lot during the whole period implying to control additional so2 emission become more costly the positive morishima substitution elasticity suggests there may exist the win win opportunities for so2 regulation moreover the large regional disparity highlights the needs to adopt a differentiated regional policy

trade and invasive species risk mitigation reconciling wto compliance with maximising the gains from trade abstract this paper analyses the issue of balancing the gains from trade with the risk of pest and disease transference two decision frameworks for determining whether or not to permit trade in a potentially invasive species carrying good are presented the first considers only the potential production losses resulting from an invasive species entering through a trade pathway as is prescribed by wto compliance the second is a unilateral welfare maximising approach which considers the consumer gains from trade the loss of domestic producers market share and expected damage from the invasive species it is shown that these alternative decision frameworks can be reconciled such that they produce the same outcome regarding whether or not trade is to be permitted the key parameters which influence these decisions are also highlighted

climate change and agriculture in developing countries most analysts agree that the poorest countries agricultures are likely to be the most vulnerable to and least capable of adapting to climate change or other environmental disruptions research has only recently begun to assess what the likely impacts of climate change on developing countries agricultures may be how these agricultures might adapt to climate change and how policies might be designed to facilitate adaptation this paper begins with a discussion of what researchers currently believe the impacts of climate change could be on developing country agriculture principally tropical agriculture climate changes are expected to occur from thirty to more than one hundred years in the future these time horizons mean that predictions of the key factors determining impacts and adaptation population income institutions and technology are probably as uncertain as predictions of climate change itself rates of productivity growth and technological adaptation will be critical to future food supplies with or without climate change continuation of the trend of the past forty years could make so abundant that climate change effects would be inconsequential but lower rates of growth could result in population growth outstripping food supplies the second section of this paper addresses the critical issue of predicting the long term trend inmore productivity by building on the substantial knowledge we have about the economic factors determining agricultural innovation and adaptation considering the time horizons and uncertainties involved in climate change the wise policy strategy is to pursue investments that are economically justified whether or not climate change occurs a better understanding of managed ecosystems would improve our understanding of agricultural sustainability as well as climate change impacts and adaptation the third section of this paper outlines an economic approach to modeling managed ecosystems 21 refs less

the impact of skewness and fat tails on the asset allocation decision the authors modeled the non normal returns of multiple asset classes by using a multivariate truncated levy flight distribution and incorporating non normal returns into the mean conditional value at risk m cvar optimization framework in a series of controlled optimizations they found that both skewness and kurtosis affect the m cvar optimization and lead to substantially different allocations than do the traditional mean variance optimizations they also found that the m cvar optimization would have been beneficial during the 2008 financial crisis

an alternative test of the capital asset pricing model reply in our 1980 paper we tested the joint hypothesis that prices are determined by the mean variance mv capital asset pricing model capm and that beliefs are stationary by focusing on the invariance law of prices we avoided the questionable practice of estimating ex ante expectations with ex post returns moreover we circumvented the need to identify the true market portfolio and hence avoided the ambiguity noted by richard roll 1977 in the traditional security market line sml tests of the same joint hypothesis however stuart turnbull and ralph winter t w and richard sweeney point to a further inconsistency in the joint hypothesis that they believe can be removed by relaxing the stationarity assumption this new concern is fundamental in that it applies to all empirical tests which assume stationarity of the return distribution whether they are simply tests of the capm or tests employing the capm the concern would apply a fortiori to tests that assume stationary betas as well both comments also suggest that the ad hoc addition of a random error term to our invariance law equation and the subsequent statistical tests of it are unnecessary we first address these two criticisms and then address some further criticisms raised separately by t w and sweeney

dynamic sanitary and phytosanitary trade policy this paper characterizes the optimal use of sanitary and phytosanitary standards to prevent the introduction of harmful pests and diseases through international trade because established pest and disease infestations grow and spread over time their introduction has intertemporal consequences in a dynamic economic model an efficient trade policy balances the costs of sps measures against the discounted stream of the costs of control and social damages that are avoided by using sps measures where future growth of any established infestation is accounted for we examine when phytosanitary trade policy makes good economic sense when it is efficient to provide full protection against pests and diseases and when restrictive but not fully protective trade policy is efficient

normality solvency and portfolio choice this paper examines whether investors with power utility functions choose mean vari ance mv efficient portfolios when returns are approximately normally distributed and there is borrowing or lending at a riskless interest rate the results show that the unlevered portfolios of power utility investors plot very closely to the mv efficient frontier how ever there are marked differences in the mix of risky assets regardless of whether the portfolios are highly concentrated or widely diversified such differences allow power investors to remain solvent even when they lever their optimal portfolios to a greater ex tent than less risk averse mv investors who risk bankruptcy it is concluded that the investment policies of power utility and mv investors with similar risk aversion measures are not as similar as is commonly believed this is particularly true for high power inves tors unless explicit solvency constraints are imposed on the mv problem and for low power investors when quadratic utility approximations are made to the power utility func tions these differences in the investment policies of power utility and mv investors lead us to question the widely accepted assertion that the assumptions of homogeneous beliefs normality a riskless asset and risk averse investors imply the simple mv capm where all investors including power utility investors hold combinations ofthe market portfolio and the riskless asset

massaging mean variance inputs returns from alternative global investment strategies in the 1980s this paper explores the impact of adjustments to the inputs on total returns terminal wealth and portfolio turnover in an unconstrained monthly mean variance mv asset allocation over time it is well known that mv allocations are very sensitive to small forecast errors in the means and covariances this sensitivity is especially pronounced for errors in means one way to control this sensitivity to forecast errors is to use stein estimation we examined three naive applications of stein estimation for six individual country stock indexes five country bond indexes and five cash indexes this study has two major conclusions first any of the suggested adjustments to inputs dominate the results of an unadjusted input mv optimization adjusted input portfolios have higher mean return less variance and greater terminal wealth than unadjusted input portfolios second these improvements become even greater with transaction costs

the mean variance optimization puzzle security portfolios and food portfolios the markowitz mean variance optimization framework presents a puzzle although it is the standard model of portfolio construction investors rarely use it and when used it is constrained so much that portfolios reflect the constraints more than the optimization why do investors dislike unadulterated optimized mean variance portfolios the typical answer focuses on biases introduced by estimation errors more important is the fact that investors goals are quite different from mean variance optimization people care about more than cost and nutrition when they construct their diets they also care about palatability similarly investors care about more than expected returns and variance as they construct their securities portfolios they also care about the investment equivalent of palatability we use an analogy between security portfolios and food portfolios to explore the nature of the gap between intuitively appealing portfolios and mean variance optimized portfolios

multivariate stochastic volatility via wishart processes financial models for asset and derivatives pricing risk management portfolio optimization and asset allocation rely on volatility forecasts time varying volatility models such as generalized autoregressive conditional heteroscedasticity and stochastic volatility svol have been successful in improving forecasts over constant volatility models we develop a new multivariate svol framework for modeling financial data that assumes covariance matrices stochastically varying through a wishart process in our formulation scalar variances naturally extend to covariance matrices rather than to vectors of variances as in traditional svol models model fitting is performed using markov chain monte carlo simulation from the posterior distribution because of the model s complexity an efficiently designed gibbs sampler is described that produces inferences with a manageable amount of computation our approach is illustrated on a multivariate time series of monthly industry portfolio returns a test of the ec

on the sensitivity of mean variance efficient portfolios to changes in asset means some analytical and computational results tbis paper investigates the sensitivity of meanvariance mv efficientportfolios to changes in the means of individual assets when only a budget constraint is imposed on the investment problem the analytical results indicate that an mv efficient portfolio s weights mean and variance can be extremely sensitive to cbanges in asset means when nonnegativity constraints are also imposed on the problem the computational results confirm that a positively weigbted mv efficient portfolio s weigbts are extremely sensitive to cbanges in asset means but the portfolio s returns are not a surprisingly small increase in the mean of just one asset drives balf the securities from the portfolio yet the portfolio s expected return and standard deviation are virtually uncbanged this paper supersedes should investors hold well diversified portfolios financial support from the natural science and engineering research council of canada is gratefully acknowledged we also acknowledge the most capable assistance of ruth cornale simon ng jean marc potier and frederick shen the paper was presented at simon fraser university and the western finance association meetings in san diego we thank the participants especially stephen brown john herzog john heaney ray koopman and bruce lehmann and the editors jon ingersoll and chester spatt for

a note on portfolio selection with restrictions on leverage abstract this note focuses on a mean variance asset allocation framework having restrictions on leverage namely where investors are constrained either to hold funds in a risk free asset i e to lend or to hold debt i e to borrow it is shown that the optimal portfolio in a constrained leverage situation will not have the same composition as the optimal portfolio in an unconstrained situation we give formal justification for the intuitive notion that the more debt an investor is constrained to hold the more the investor should tilt the remaining investments towards a portfolio of less risky assets conversely the greater the proportion an investor is constrained to hold in a risk free asset the more the investor should tilt remaining investment towards a portfolio of more risky assets

avoiding invasives trade related policies for controlling unintentional exotic species introductions abstract international commodity trade serves as the primary conduit for unintentional introductions of damaging exotic species we use a simple model of contaminated goods trade to analyze the optimal mix of tariffs and inspections as means of controlling damage from this negative externality among other policy relevant results we find that 1 while it is always optimal to employ tariffs there are non trivial cases in which inspections should optimally be set to zero 2 a higher infection rate requires a higher tariff but beyond a point optimal inspections decrease in the infection rate and finally 3 taking a dynamic view and considering future effects of current introductions leads unambiguously to more stringent inspections but may give rise to higher or lower tariffs

the effect of ambiguous risk and coordination on farmers adaptation to climate change a framed field experiment the risk of losses of income and productive means due to adverse weather can differ significantly among farmers sharing a productive landscape and is of course hard to estimate or even guesstimate empirically moreover the costs associated with investments in reduced vulnerability to climatic events are likely to exhibit economies of scope we explore the implications of these characteristics on farmer s decisions to adapt to climate change using a framed field experiment applied to coffee farmers in costa rica as expected we find high levels of risk aversion but even using that as a baseline we further find that farmers behave even more cautiously when the setting is characterized by unknown or ambiguous risk i e poor or non reliable risk information secondly we find that farmers to a large extent coordinated their decisions to secure a lower adaptation cost and that communication among farmers strongly facilitated coordination

marginal abatement costs of carbon dioxide emissions in china a parametric analysis this paper investigates the technical inefficiency shadow price and substitution elasticity of hbox co 2 emissions of china based on a provincial panel for 2001 2010 using linear programming to calculate a quadratic parameterized directional output distance function we show that china s technical inefficiency increases over the period implying further scope for hbox co 2 emissions reduction in the medium and longer term at best by 4 5 and 4 9 respectively our results notwithstanding regional differences highlight increases in the shadow price of hbox co 2 abatement 1 000 yuan ton in 2001 to 2 100 yuan ton in 2010 additionally increasingly steep substitution elasticity highlights the difficult reality of reducing china s hbox co 2 emissions

the intercountry agricultural production function another view factor productivity in agriculture is estimated from repeated observations on a sample of fifty eight countries under the assumption that all countries have access to the same technology technology is viewed as a collection of techniques each technique is represented by a production function the choice of the implemented techniques is determined by the state variables which represent the physical and economic environment within which the firms operate the statistical model is that of varying coefficients and it is estimated by a method which utilizes principal components and multiple comparisons

downside versus symmetric measures of uncertainty in natural resource portfolio design to manage climate change uncertainty recent work uses markowitz s mean variance framework to identify efficient allocations of conservation activity across subregions of a planning landscape to minimize climate change induced uncertainty in future conservation benefits we replace variance with a downside measure of uncertainty and compare the resulting portfolios of conservation activity and uncertainty expected value results against those generated by the mean variance approach results illustrate that conservation agents can manage climate changed induced uncertainty in future conservation outcomes more efficiently using our framework when they are particularly averse to downside uncertainty and when predicted future conservation outcomes within subregions across their planning horizon exhibit skewed distributions

co2 emission abatement cost and its decomposition a directional distance function approach accurately estimating carbon dioxide co2 abatement costs and effectively identifying the factors impacting those costs can improve the applicability and effectiveness of policy implementation this paper proposes a new method to estimate co2 abatement costs cac based on the directional distance function the method theoretically decomposes cac into carbon productivity and output elasticity of substitutions this decomposition can identify the types of cac the method also investigates the effects of development mode selection on cac by selecting different directional vectors following the theoretical discussion an empirical study is presented focusing on high energy consumption firms in the united states u s the results were as follows 1 in sustainable development mode changes in the average cac of all firms were caused both by carbon productivity and output elasticity of substitution carbon productivity dominated cac differences among different firm types 2 in general the amelioration potential of firm technology and environmental management was gradually explored by firms during sample period corresponding environmental regulatory strategies are needed for firms with different cac characteristics 3 firms selecting different development modes will realize significant differences in cac firms in the sustainable development mode had the highest cac levels however this mode was best for achieving a win win between economic benefits and environmental protection

bayesian estimation of the global minimum variance portfolio in this paper we consider the estimation of the weights of optimal portfolios from the bayesian point of view under the assumption that the conditional distribution of the logarithmic returns is normal using the standard priors for the mean vector and the covariance matrix we derive the posterior distributions for the weights of the global minimum variance portfolio moreover we reparameterize the model to allow informative andnon informative priors directly for the weights of the global minimum variance portfolio the posterior distributions of the portfolio weights are derived in explicit form for almost all models the models are compared by using the coverage probabilities of credible intervals in an empirical study we analyze the posterior densities of the weights of an international portfolio

the transition of punjab agriculture a choice of technique approach the introduction of modern crop varieties in punjab india led to rapid income growth adoption rate and level of the new varieties is examined using a choice of technique approach in which techniques of production are identified by crop variety season of growth and method of production modeling the dynamic effects of technology resource availability and incentives reveals a consistent picture of the transition process the results show the importance of incentives and availability of quasi fixed inputs such as irrigation fertilizers and roads by the late 1970s the long run aggregate supply elasticity was between 1 3 1 5

the impact of global warming on agriculture a ricardian analysis reply we measure the economic impact of climate on land prices using cross sectional data on climate farmland prices and other economic and geophysical data for almost 3 000 counties in the united states we find that higher temperatures in all seasons except autumn reduce average farm values while more precipitation outside of autumn increases farm values applying the model to a global warming scenario shows a significantly lower estimated impact of global warming on u s agriculture than the traditional production function approach and in one case suggests that even without co sub 2 fertilization global warming may have economic benefits for agriculture 16 refs 5 figs 5 tabs

argentine agricultural policy in a multiple input multiple output framework argentine agricultural output grew at a rate of about 1 4 per year between 1940 and 1972 cavallo and mundlak p 13 which is a very sluggish growth rate given earlier rates of 1 8 for 1908 20 and 2 2 1920 40 schultz it also is sluggish relative to growth in u s agricultural output of 1 9 during the same period adjusting for factor use total factor productivity in argentine agriculture grew at a rate of only 0 6 during this period compared to 1 2 in the rest of the argentine economy cavallo and mundlak and compared to about 1 9 in u s agriculture usda a number of hypotheses have been offered to

portfolio management with robustness in both prediction and decision a mixture model based learning approach abstract we develop in this paper a novel portfolio selection framework with a feature of double robustness in both return distribution modeling and portfolio optimization while predicting the future return distributions always represents the most compelling challenge in investment any underlying distribution can be always well approximated by utilizing a mixture distribution if we are able to ensure that the component list of a mixture distribution includes all possible distributions corresponding to the scenario analysis of potential market modes adopting a mixture distribution enables us to 1 reduce the problem of distribution prediction to a parameter estimation problem in which the mixture weights of a mixture distribution are estimated under a bayesian learning scheme and the corresponding credible regions of the mixture weights are obtained as well and 2 harmonize information from different channels such as historical data market implied information and investors subjective views we further formulate a robust mean cvar portfolio selection problem to deal with the inherent uncertainty in predicting the future return distributions by employing the duality theory we show that the robust portfolio selection problem via learning with a mixture model can be reformulated as a linear program or a second order cone program which can be effectively solved in polynomial time we present the results of simulation analyses and primary empirical tests to illustrate a significance of the proposed approach and demonstrate its pros and cons

risk forecasting models and optimal portfolio selection this study analyses from an investor s perspective the performance of several risk forecasting models in obtaining optimal portfolios the plausibility of the homoscedastic hypothesis implied in the classical markowitz model is dicussed and more general models which take into account assymetry and time varying risk are analysed specifically it studies whether arch type based models obtain portfolios whose risk adjusted returns exceed those of the classical markowitz model the same analysis is performed with models based on the lower partial moment lpm which take into account the assymetry in the distribution of returns the results suggest that none of the models achieve a clearly superior average performance it is also found that models based on semivariance perform as well as those based on the variance but not better than even if the evaluation criterion is based on the reward to semivariance ratio when attention turns to the analysis of worst case performance the results are clearly differ

there is no silver bullet the value of diversification in planning invasive species surveillance abstract in this study we demonstrate how the notion of diversification can be used in broad scale resource allocation for surveillance of invasive species we consider the problem of short term surveillance for an invasive species in a geographical environment we find the optimal allocation of surveillance resources among multiple geographical subdivisions via application of a classical portfolio framework which allocates investments among multiple financial asset types with uncertain returns in a portfolio that maximizes the performance and by meeting the desired diversification targets protects against errors in estimating the portfolio s performance we illustrate the approach with a case study that applies a spatial transmission model to assess the risk of spread of the emerald ash borer eab a significant pest in north america with infested firewood that may be carried by visitors to campground facilities in central canada adding the diversification objective yields an expected survey performance that is comparable with undiversified optimal allocation but more importantly makes the geographical distribution of survey priorities less subject to possible errors in the spread rate estimates overall diversification of pest surveillance can be viewed as a viable short term strategy for hedging against uncertainty in expert and model based assessments of pest invasion risk

marginal abatement costs of carbon dioxide emissions and its influencing factors a global perspective abstract reducing co 2 emissions has become a major and urgent environmental goal worldwide in this paper we sample the data of 41 regions including 165 countries from 2000 to 2014 and adopt a gravity model to obtain an overview of the global flows of co 2 emissions energy consumption the global economy and capital stock since the beginning of the 21st century we then investigate global technical efficiency reduction potential shadow prices and factors influencing the marginal abatement costs of co 2 emissions based on a quadratic directional output distance function the empirical results show the following 1 the global centres of gravity for co 2 emissions energy consumption and capital stock have accelerated their shift to the asian inland in the 21st century but the global centre of gravity for the economy did not show the same trend 2 global technical inefficiency demonstrates a u shape with a turning point in 2007 average annual total global co 2 emissions could be reduced by 4482 28 mt and the global marginal abatement costs of co 2 emissions are approximately 673 74 697 73 usd t 3 the relationship between economic development and marginal abatement costs is represented by a u shaped curve the world is currently in the climbing phase of this curve implying that controlling co 2 emissions is becoming more costly moreover energy structure industrial structure and co 2 emissions are negatively correlated with marginal abatement costs finally the financial crisis has had a significant effect on marginal abatement costs

60 years of portfolio optimization practical challenges and current trends abstract the concepts of portfolio optimization and diversification have been instrumental in the development and understanding of financial markets and financial decision making in light of the 60 year anniversary of harry markowitz s paper portfolio selection we review some of the approaches developed to address the challenges encountered when using portfolio optimization in practice including the inclusion of transaction costs portfolio management constraints and the sensitivity to the estimates of expected returns and covariances in addition we selectively highlight some of the new trends and developments in the area such as diversification methods risk parity portfolios the mixing of different sources of alpha and practical multi period portfolio optimization

how many stocks make a diversified portfolio we show that a well diversified portfolio of randomly chosen stocks must include at least 30 stocks for a borrowing investor and 40 stocks for a lending investor this contradicts the widely accepted notion that the benefits of diversification are virtually exhausted when a portfolio contains approximately 10 stocks we also contrast our result with the levels of diversification found in studies of individuals portfolios

active portfolio management with benchmarking adding a value at risk constraint abstract we examine the impact of adding a value at risk var constraint to the problem of an active manager who seeks to outperform a benchmark while minimizing tracking error variance tev by using the model of roll 1992 a mean variance analysis of tracking error journal of portfolio management 18 13 22 we obtain three main results first portfolios on the constrained mean tev boundary still exhibit three fund separation but the weights of the three funds when the constraint binds differ from those in roll s model second the constraint mitigates the problem that when an active manager seeks to outperform a benchmark using the mean tev model he or she selects an inefficient portfolio finally when short sales are disallowed the extent to which the constraint reduces the optimal portfolio s efficiency loss can still be notable but is smaller than when short sales are allowed

do constraints improve portfolio performance the discrete time dynamic investment model using only historical data in various asset allocation settings often produces significant abnormal returns however the model does not choose the diversified portfolios that theory suggests it should therefore in this paper we compare the investment policies and returns of the model with and without constraints on the mix of risky assets the constraints lead to appreciably more diversification and less realized risk but only at the cost of less realized return visual comparisons of compound return standard deviation plots and statistical comparisons of jensen s alpha suggest that the reduction in return is not worth the reduction in risk for more risk averse investors ex post utility and certainty equivalent returns suggest that it is the results however illustrate the problems associated with using ex post utility to measure performance 2000 elsevier science b v all rights reserved

portfolio selection under distributional uncertainty a relative robust cvar approach robust optimization one of the most popular topics in the field of optimization and control since the late 1990s deals with an optimization problem involving uncertain parameters in this paper we consider the relative robust conditional value at risk portfolio selection problem where the underlying probability distribution of portfolio return is only known to belong to a certain set our approach not only takes into account the worst case scenarios of the uncertain distribution but also pays attention to the best possible decision with respect to each realization of the distribution we also illustrate how to construct a robust portfolio with multiple experts priors by solving a sequence of linear programs or a second order cone program

optimal border policies for invasive species under asymmetric information this paper analyzes the problem faced by a border protection agency if endogenous exporter abatement activities affect invasive species risk allowing for unobservable differences in abatement cost we show how the optimal inspection penalty regime differs from the symmetric information case departing from previous literature we allow for technical assistance a policy instrument specifically permitted and commonly employed under article 9 of the world trade organization sanitary and phytosanitary agreement we find the information asymmetry can make it optimal for the importing country to provide technical assistance grants for exporter risk abatement even if it would otherwise be inefficient further we show that fungibility of technical assistance with inputs in other sectors of the exporting economy affects the qualitative nature of optimal policy if technical assistance has no outside value in the exporter s country optimal policy is characterized by a menu of contracts balancing higher tariffs with lower penalties for being caught with an invasive if technical assistance can be used in other sectors of the exporter s economy it can introduce countervailing incentives making a uniform tariff penalty combination optimal

in defense of portfolio optimization what if we can forecast author response we thank richard o michaud david n esch and robert o michaud for their interest in our paper in their letter they suggest that our results are inconsistent with the canonical literature beca

tariff escalation and invasive species damages we investigate the interface between trade and damages from invasive species is focusing on escalation in tariffs between raw input and processed good markets and its implication for is based damages the current tariff escalation in processed agro forestry products motivates our analysis tariff escalation exacerbates the likelihood of is introduction by biasing trade flows towards increased trade of primary commodity flows and against processed product trade we show that a reduction of tariff escalation by lowering the tariff on processed goods increases allocative efficiency and reduces is based damages a win win situation we also identify policy menus for trade reforms involving tariffs on both raw input and processed goods leading to win win situations

general uncertainty in portfolio selection a case based decision approach abstract often a portfolio investor can hardly imagine all states of nature relevant to his investment problem causing general uncertainty concerning an asset allocation model we quantify general uncertainty as the weakness of an investor s belief in a conventional portfolio procedure then we develop the case based decision making approach for determining the optimal belief degree the economic effect of the proposed case based methodology is investigated in the empirical study the empirical results suggest two successful patterns of case based decisions that could be linked to the issue of market efficiency moreover our case based modeling reflects some behavioral phenomena observed on financial markets

valuing social sustainability in agriculture an approach based on social outputs shadow prices abstract interest in sustainability has gained ground among practitioners academics and policy makers due to growing stakeholders awareness of environmental and social concerns this is particularly true for agriculture however relatively little research has been conducted on the quantification of social sustainability and the contribution of social issues to the agricultural production efficiency this paper proposes a framework based on state contingent outputs to compute shadow prices of social outputs our methodological approach is based on the directional distance function and illustrated using a farm level dataset from a sample of catalan arable crop farms in 2015 our results indicate that in the sample of 180 farms included in the analysis efficiency scores are relatively high for the three alternative states of the nature considered in our state contingent analysis in addition our findings show that social outputs shadow prices are positive indicating that producing more social outputs is considered as great value to the farm for the efficient farms the social outputs shadow prices are contingent upon on the state of nature in a way that social outputs shadow prices increase with the improvement in crop growth conditions these results have implications in terms of eu farm payment redistribution

in defense of optimization the fallacy of 1 n previous research has shown that equally weighted portfolios outperform optimized portfolios which suggests that optimization adds no value in the absence of informed inputs this article argues the opposite with naive inputs optimized portfolios usually outperform equally weighted portfolios the ostensible superiority of the 1 n approach arises not from limitations in optimization but rather from reliance on rolling short term samples for estimating expected returns this approach often yields implausible expectations by relying on longer term samples for estimating expected returns or even naively contrived yet plausible assumptions optimized portfolios outperform equally weighted portfolios out of sample

the sampling error in estimates of mean variance efficient portfolio weights this paper presents an exact finite sample statistical procedure for testing hypotheses about the weights of mean variance efficient portfolios the estimation and inference procedures on efficient portfolio weights are performed in the same way as for the coefficients in an ols regression ols t and f statistics can be used for tests on efficient weights and when returns are multivariate normal these statistics have exact t and f distributions in a finite sample using 20 years of data on 11 country stock indexes we find that the sampling error in estimates of the weights of a global efficient portfolio is large

the shadow prices of co2 and so2 for chinese coal fired power plants a partial frontier approach abstract shadow prices are widely employed in guiding environmental policies this paper contributes to the literature by developing a novel partial frontier approach for estimating shadow prices the proposed method is advanced in handling outliers and provides a precise estimation of the marginal rate of substitution along the production frontier to cope with the different disposability characteristics of undesirable emissions so2 is treated as an environmental input that is strongly disposable because most different undesirable outputs are jointly reduced this study is the first to use directional derivatives instead of partial derivatives and proposes a new separation method that separates individual directional shadow price from the cost of joint reduction of multiple undesirable outputs we apply the proposed method to a sample of 93 coal fired power plants covering six years the estimated average shadow prices of co2 and so2 are 69 tonne and 2525 tonne under the newly developed partial frontiers when assuming some undesirable output to be strongly disposable both shadow prices fall 20 32 tonne and 1018 23 tonne the present paper suggests the estimated shadow prices will be much different across different levels of disposability the cost of joint reduction is calculated as 91 05 unit given the current production level which leads to a directional shadow price for the two undesirable outputs of 91 32 tonne and 1250 06 tonne the estimated shadow prices for both undesirable outputs dispersed widely under the partial frontiers spatial distribution of estimated shadow prices shows that coastal provinces and municipalities have higher co2 shadow prices but lower so2 shadow prices whereas the northeast provinces are the opposite the co2 shadow price is comparatively stable over the study period while the so2 shadow price fluctuates policy implications are discussed

keynes meets markowitz the trade off between familiarity and diversification we develop a model of portfolio choice to nest the views of keynes who advocates concentration in a few familiar assets and markowitz who advocates diversification we use the concepts of ambiguity and ambiguity aversion to formalize the idea of an investor s familiarity toward assets the model shows that for any given level of expected returns the optimal portfolio depends on two quantities relative ambiguity across assets and the standard deviation of the expected return estimate for each asset if both quantities are low then the optimal portfolio consists of a mix of familiar and unfamiliar assets moreover an increase in correlation between assets causes an investor to increase concentration in familiar assets flight to familiarity alternatively if both quantities are high then the optimal portfolio contains only the familiar asset s as keynes would have advocated in the extreme case in which both quantities are very high no risky asset is held nonparticipation this paper was accepted by brad barber teck ho and terrance odean special issue editors

an analytic derivation of admissible efficient frontier with borrowing the admissible efficient portfolio selection problem for risky assets has been discussed by zhang and nie in this paper the admissible efficient portfolio model is proposed under the assumption that there exists the borrowing money or a risk free asset case the admissible efficient frontiers are developed by the spreads of expected return and risk from admissible errors the analytic forms of the admissible efficient frontiers when short sales are not allowed on all risky assets are derived from two cases the borrowing with an upper bound constraint or without an upper bound constraint the influence on the admissible efficient frontier is explained under the different interest rates of the borrowing the differences between the results with the borrowing and the results without the borrowing is revealed by a real numerical example

capital asset pricing compatible with observed market value weights we show that the set of expected return vectors for which an observed portfolio is mean variance mv efficient is a two parameter family we identify ten ways to specify the time series behavior of the two parameters the result highlights a number of inconsistencies involved in mv modelling for each of the cases it permits the inference of the time series of expected return vectors as well as all the other capital asset pticing model capm variables compatible with a known covariance matrix and the observed time series of market value weights the empirical work shows that there are substantial case to case differences in the time series of mean vectors and many of them are quite different from the constant mean vector envisioned in tests of

measuring environmental efficiency of industry a case study of thermal power generation in india technical and environmental efficiency of some coal fired thermal power plants in india is estimated using a methodology that accounts for firm s efforts to increase the production of good output and reduce pollution with the given resources and technology the methodology used is directional output distance function estimates of firm specific shadow prices of pollutants bad outputs and elasticity of substitution between good and bad outputs are also obtained the technical and environmental inefficiency of a representative firm is estimated as 0 06 implying that the thermal power generating industry in andhra pradesh state of india could increase production of electricity by 6 while decreasing generation of pollution by 6 this result shows that there are incentives or win win opportunities for the firms to voluntarily comply with the environmental regulation it is found that there is a significant variation in marginal cost of pollution abatement or shadow prices of bad outputs across the firms and an increasing marginal cost of pollution abatement with respect to pollution reduction by the firms this result calls for the use of economic instruments like pollution taxes instead of command and control regulation used currently in india to reduce air pollution

improving diversification opportunities for socially responsible investors socially responsible investment sri has grown enormously and has expanded globally in recent years it allows sri investors to reduce their portfolio risk assumptions through international diversification in this context the aim of this paper is twofold i to examine price and volatility linkages among the most representative sri indexes for north america europe and asia pacific employing a multivariate approach and ii to provide the out of sample performance of an optimal portfolio constructed on the basis of time varying return and volatility forecasts from this specification approach our overall results show that using this technique it is possible to reduce risk and out perform the naive rule which is usually employed in this type of investment these findings are relevant not only for academics but also for practitioners especially for professional managers of sri portfolios

sulfur dioxide control in china policy evolution during the 10th and 11th five year plans and lessons for the future china s central government established national goals to reduce sulfur dioxide so2 emissions by 10 in both the 10th and 11th five year plan periods 2001 2005 and 2006 2010 respectively but the early policies were unsuccessful at reducing emissions emissions increased 28 during the 10th five year plan after adapting a number of policies and introducing new instruments during the 11th five year plan so2 emissions declined by 14 we examine the evolution of these policies their interplay with technical and institutional factors and capture lessons from the 11th five year plan to guide future pollution control programs we find that several factors contributed to achievement of the 11th five year plan so2 reduction goal 1 instrument choice 2 political accountability 3 emission verification 4 political support 5 streamlined targets and 6 political and financial incentives the approach integrated multiple policy instruments market based command and control and administrative instruments specific to the chinese context the evolution of so2 reduction policies and programs has implications for further so2 reductions from power plants and other sources as well as control of other atmospheric pollutants such as nitrogen oxides nox and carbon dioxide co2 in china

the dynamic black litterman approach to asset allocation abstract we generalize the black litterman bl portfolio management framework to incorporate time variation in the conditional distribution of returns in the asset allocation process we evaluate the performance of the dynamic bl model using both standard performance ratios as well as other measures that are designed to capture tail risk in the presence of non normally distributed asset returns we find that the dynamic bl model outperforms a range of different benchmarks moreover we show that the choice of volatility model has a considerable impact on the performance of the dynamic bl model

portfolio analysis with a large universe of assets covariance matrix optimization algorithms are applied to a large number of assets a previous paper by burgess and bey 1988 suggests that attempting to optimize a large number of securities with the traditional covariance matrix model is not practical an alternative approach ranks the securities with the reward to volatility reward to beta ratio and then optimizes a smaller subset of securities with the covariance matrix model this study proposes additional screening methods such as stochastic dominance reward to variability r v ratios reward to lower partial moment r lpm ratios and the optimization of subgroups and provides an empirical test of the various screening methodologies the results indicate that the full covariance critical line optimization algorithm is surprisingly robust compared to the other techniques

tariffs and the risk of invasive pest introductions in commodity imports theory and empirical evidence abstract we investigate using tariffs as corrective taxes to reduce risks from biological invasions due to expanded world trade a theoretical analysis indicates that higher tariffs have ambiguous effects on invasive pest introductions an econometric analysis using data from us department of agriculture surveillance screening indicates that tariff rates exert a negligible influence on expected invasive pest introductions from commodities currently facing positive tariffs removal of duty free status would decrease expected pest intercepts but undermine other goals of us trade policy and lower consumer welfare consumer welfare loss is on the order of 38 million per expected intercept avoided

more possessions more worry abstract a common wisdom asserts that the wider the universe of assets to choose from the greater the investor s welfare we show that this is not the case in practice where parameters have to be estimated even when the estimates are unbiased surprisingly risk aversion plays a crucial role corresponding to the desirability of asset expansion by dividing investors in three groups investors with very low risk tolerance and investors with very high risk tolerance are better off with asset expansion and investors with moderate risk tolerance are worse off despite the option to refrain from investing in the additional asset

interactions between agricultural and environmental policies a conceptual framework agricultural policy has a well documented impact on farmers production decisions and those decisions land water and agricultural chemical use may in turn affect the environment there is a public perception that existing agricultural policies are linked to agricultural pollution as exemplified by the conclusions of the recent national research council report alternative agriculture 1989 there is only limited theoretical or empirical research addressing these linkages however this paper develops a conceptual framework that can be used to analyze the interactions between agricultural and environmental policies and pollution this framework integrates physical and economic models at a disaggregate level necessary to capture the heterogeneity of the physical environment and the economic behavior of farmers following e hochman and d zilberman 1978 the disaggregate units can be statistically aggregated to a level useful for policy analysis agricultural and environmental policies can be categorized according to their effects on the intensive and extensive margins combining the different policy instruments with the microeconomic heterogeneity we find that existing agricultural and environmental policies can have either positive or negative effects of nonpoint source pollution to infer an aggregate effect requires data that do not currently exist our framework provides a basis for empirical investigations of these effects given adequate data moreover we find that agricultural policy instruments can be used to mitigate pollution if used appropriately

asset allocation with correlation a composite trade off abstract we assess the ability of minimum variance portfolio allocation strategies accounting for time varying correlation between assets to provide performance benefits relative to an equally weighted portfolio prior to transaction costs correlation based strategies emphatically outperform the equally weighted benchmark this finding is strongest for short horizon correlation forecasts and attributed to dynamic correlation as opposed to variance forecasts thus estimation error is not found to be the primary obstacle to successful portfolio optimization rather frequent rebalancing and associated transaction costs pose a significant challenge limiting portfolio turnover through short selling restrictions and greater rebalancing error tolerance results in regular outperformance of the correlation based strategies even for large transaction costs taken together these findings provide evidence of a trade off between optimal portfolio performance forecasting horizon rebalancing frequency and transaction costs