robust portfolio optimization for electricity planning an application based on the brazilian electricity mix one of the major challenges of today s policy makers and industry strategists is to achieve an electricity mix that presents a high level of energy security within a range of affordable costs and environmental constraints bearing in mind the planning of a more reliable electricity mix the main contribution of this paper is to consider parameter uncertainties on the electricity portfolio optimization problem we assume that the expected and the covariance matrix of the costs for the different energy technologies such as gas coal nuclear oil biomass wind large and small hydropower are not exactly known we consider that these parameters belong to some uncertainty sets box ellipsoidal lower and upper bounds and convex polytopic three problems are analyzed i finding a energy portfolio of minimum worst case volatility with guaranteed fixed maximum expected energy cost ii finding an energy portfolio of minimum worst case expected cost with guaranteed fixed maximum volatility of the energy cost iii finding a combination of the expected and variance of the cost weighted by a risk aversion parameter these problems are written as quadratic second order cone programming socp and semidefinite programming sdp so that robust optimization tools can be applied these results are illustrated by analyzing the efficient brazilian electricity energy mix considered in losekann et al 2013 assuming possible uncertainties in the vector of expected costs and covariance matrix the results suggest that the robust approach being by nature more conservative can be useful in providing a reasonable electricity energy mix conciliating co2 emission risk and costs under uncertainties on the parameters of the model

renegotiation and the efficiency of investments in a long term relationship between two parties one party s threat of a unilateral violation of an initial contract may induce a renegotiation of the contract as a renegotiation may result in one party capturing some of the return from the other s investments this possibility may lead to underinvestment i show that if there is uncertainty associated with the outcome of a renegotiation and if players are risk averse there will be an interval for the initial contract so that it is not renegotiated by an appropriate choice of the initial contract underinvestment can thus be avoided

contract renewal under uncertainty abstract the incentive to adjust prices is considered from a bilateral perspective in a setting where changes in outside opportunities drive the incentive to renew contracts and costs preclude continuous renewal a model encompassing several contract forms is formulated and the existence of an equilibrium to the bilateral renewal game is established prices display inertia and the incumbent contract is found to be more resistant to changes in outside opportunities the larger the costs of contract renewal the variability of outside opportunities and the lower the discount rate the model is shown to match a number of empirical observations on contracts

scenario modelling for selective hedging strategies abstract we study currency risk management in the context of scenario analysis we develop scenario based optimization models that jointly determine the portfolio composition and the hedging strategy within each currency thus the model prescribes optimal selective hedging policies we then study empirically the performance of the models the new elements of our empirical analysis are various horizons one month and one semester various currency bases explicit incorporation of realistic transaction costs the results show that selective hedging strategies dominate the alternatives under some conditions and that transaction costs are very important in determining the profitability of various currency risk management strategies for both stocks and bonds at the one month horizon

portfolio selection with uncertain exit time a robust cvar approach abstract in this paper we explore the portfolio selection problem involving an uncertain time of eventual exit to deal with this uncertainty the worst case cvar methodology is adopted in the case where no or only partial information on the exit time is available and the corresponding problems are integrated into linear programs which can be efficiently solved moreover we present a method for specifying the uncertain information on the distribution of the exit time associated with exogenous and endogenous incentives numerical experiments with real market data and monte carlo simulation show the usefulness of the proposed model

a dynamic stochastic programming model for international portfolio management we develop a multi stage stochastic programming model for international portfolio management in a dynamic setting we model uncertainty in asset prices and exchange rates in terms of scenario trees that reflect the empirical distributions implied by market data the model takes a holistic view of the problem it considers portfolio rebalancing decisions over multiple periods in accordance with the contingencies of the scenario tree the solution jointly determines capital allocations to international markets the selection of assets within each market and appropriate currency hedging levels we investigate the performance of alternative hedging strategies through extensive numerical tests with real market data we show that appropriate selection of currency forward contracts materially reduces risk in international portfolios we further find that multi stage models consistently outperform single stage models our results demonstrate that the stochastic programming framework provides a flexible and effective decision support tool for international portfolio management

value at risk versus expected shortfall a practical perspective value at risk var has become a standard risk measure for financial risk management however many authors claim that there are several conceptual problems with var among these problems an important one is that var disregards any loss beyond the var level we call this problem the tail risk in this paper we illustrate how the tail risk of var can cause serious problems in certain cases cases in which expected shortfall can serve more aptly in its place we discuss two cases concentrated credit portfolio and foreign exchange rates under market stress we show that expected shortfall requires a larger sample size than var to provide the same level of accuracy 2004 elsevier b v all rights reserved

investments holdup and the form of market contracts the authors analyze incomplete contracts to induce efficient investment with exogenous switching costs fixed price contracts are efficient generate some rigidity in prices are renegotiated intermittently by possibly small amounts and when inflation is positive generate asymmetric responses to shocks all consistent with evidence on prices and wages with two sided specific investments efficiency requires prices to have sufficient escalator clauses to avoid renegotiation as observed in many long term contracts a third case with one sided specific investments can generate take or pay contracts and explain why firms sometimes pay for specific investments that appear to benefit employees directly

tests for parameter instability in regressions with i 1 processes this article derives the large sample distributions of lagrange multiplier lm tests for parameter instability against several alternatives of interest in the context of cointegrated regression models the fully modified estimator of phillips and hansen is extended to cover general models with stochastic and deterministic trends the test statistics considered include the supf test of quandt as well as the lm tests of nyblom and of nabeya and tanaka it is found that the asymptotic distributions depend on the nature of the regressor processes that is if the regressors are stochastic or deterministic trends the distributions are noticeably different from the distributions when the data are weakly dependent it is also found that the lack of cointegration is a special case of the alternative hypothesis considered an unstable intercept so the tests proposed here may also be viewed as a test of the null of cointegration against the alternative of no cointegration the tests are applied to three data se

mean var portfolio optimization a nonparametric approach portfolio optimization involves the optimal assignment of limited capital to different available financial assets to achieve a reasonable trade off between profit and risk we consider an alternative markowitz s mean variance model in which the variance is replaced with an industry standard risk measure value at risk var in order to better assess market risk exposure associated with financial and commodity asset price fluctuations realistic portfolio optimization in the mean var framework is a challenging problem since optimizing var leads to a non convex np hard problem which is computationally intractable in this work an efficient learning guided hybrid multi objective evolutionary algorithm mode gl is proposed to solve mean var portfolio optimization problems with real world constraints such as cardinality quantity pre assignment round lot and class constraints a learning guided solution generation strategy is incorporated into the multi objective optimization process to promote efficient convergence by guiding the evolutionary search towards promising regions of the search space the proposed algorithm is compared against the non dominated sorting genetic algorithm nsga ii and the strength pareto evolutionary algorithm spea2 experimental results using historical daily financial market data from s p 100 and s p 500 indices are presented experimental results shows that mode gl outperforms two existing techniques for this important class of portfolio investment problems in terms of solution quality and computational time the results highlight that the proposed algorithm is able to solve the complex portfolio optimization without simplifications while obtaining good solutions in reasonable time and has significant potential for use in practice

worst case robust profit in generation self scheduling recent research has shown that portfolio optimization theory can be extended to generation self scheduling in a competitive energy market this letter considers the self scheduling problem in the case where the mean vector and covariance matrix of the probability distribution of prices are only known within given bounds and the probability distribution is otherwise arbitrary under the above assumptions it is shown that a method for optimization over symmetric cones can be used to 1 compute the worst case robust profit with probability level beta and 2 optimize the self schedule for a given probability level beta of the corresponding worst case robust profit

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

the phillips curve under state dependent pricing abstract we derive a phillips curve equation from the dynamic stochastic general equilibrium dsge model with state dependent pricing developed by dotsey et al 1999 state dependent pricing and the general equilibrium dynamics of money and output quarterly journal of economics 114 655 690 this state dependent phillips curve encompasses the new keynesian phillips curve nkpc based on calvo type price setting as a special case we analyze the effect of the state dependent terms that is the variations in the distributions of price vintages on inflation persistence and we examine whether the hybrid nkpc that is the nkpc extended by a lagged inflation term can adequately describe inflation dynamics generated in a calibrated state dependent pricing economy

commodity and developing country terms of trade what does the long run show recently the debate surrounding the commodity net barter terms of trade and the terms of trade of developing countries has entered a new phase in this journal spraos i980 presents evidence of a stable declining commodity terms of trade and sapsford i985 although fl nding instability in the work of spraos argues in support of the stable declining terms of trade hypothesis grilli and yang i988 henceforth gy also provide evidence supporting this view and state the implications of this finding for developing country terms of trade a major contribution of gy is a published set of data on the main price indices with a high degree of consistency for the whole century 1 however cuddington and urzua i989 in thisjournal illustrate that the hypothesis of a secular deterioration in the commodity terms of trade is not robust to the alternative claim that there was a once and for all shift in commodity prices in the period i920 i after taking this shift into account these authors find little evidence to support the view of a secular decline 2 this debate has important implications for the prebisch singer hypothesis of a stable declining commodity terms of trade see for instance prebisch i 950 it also has implications for both development and stabilisation strategies adopted by commodity dependent developing countries a central issue in this analysis is the order of integration of the commodity terms of trade a time series is said to be integrated of order o i o if its mean and variance are constant or roughly speaking if the series is stationary a time series is said to be i n if the series requires first differencing n times before a stationary series is obtained alternatively if adding a time trend is sufficient to induce stationarity the series is termed trend stationary a trend stationary series implies that the variable in question simply adjusts around a constant growth path but an i i series is truly non stationary and displays very different properties a commonly cited example of an 1 i series is the random walk the order of integration of a single time series is related to the idea of cointegration of a number of time series consider two variables x and y that are not themselves i o but are of the same order of integration if the residuals from regressing x on y or vice versa are i o or roughly speaking if the residuals are stationary it can be concluded that the two variables are cointegrated in turn this implies that there is some form of equilibrium

robust portfolio selection using linear matrix inequalities abstract in this paper we consider the problem of robust optimal portfolio selection for tracking error when the expected returns of the risky and risk free assets as well as the covariance matrix of the risky assets are not exactly known we assume that these parameters belong to a convex polytope defined by some known elements which form the vertices of this polytope we consider two problems the first one is to find a portfolio of minimum worst case volatility of the tracking error with guaranteed fixed minimum target expected performance the second one is to find a portfolio of maximum worst case target expected performance with guaranteed fixed maximum volatility of the tracking error we show that these two problems are equivalent to solving linear matrix inequalities lmi optimization problems so that the powerful numerical packages nowadays available for this class of problems can be used a numerical example in the sao paulo stock exchange bovespa is presented

identifying terms of trade shocks in a developing country using a sign restrictions approach using annual data for botswana from 1960 to 2012 we examine the responses of macroeconomic variables to four generalized positive terms of trade shocks global demand globalizing sector specifi

delays in renewal of labor contracts theory and evidence in many countries an expired labor contract is automatically extended during the often protracted delay before the new contract is signed our theoretical model focuses on macroeconomic factors in explaining the delay it emphasizes the importance of the realized nominal and real shocks and of the levels of nominal and real uncertainty the model is tested using israeli collective wage agreements where long delays are frequent the empirical findings strongly support the theoretical model thus nominal uncertainty is found to increase the delay and real uncertainty to decrease the delay but less in the public than in the private sector

bayes stein estimation for portfolio analysis in portfolio analysis uncertainty about parameter values leads to suboptimal portfolio choices the resulting loss in the investor s utility is a function of the particular estimator chosen for expected returns so this is a problem of simultaneous estimation of normal means under a well specified loss function in this situation as stein has shown the clas sical sample mean is inadmissible this paper presents a simple empirical bayes estimator that should outperform the sample mean in the context of a portfolio simulation analysis shows that these bayes stein estimators provide significant gains in portfolio selection problems

a multi period fuzzy portfolio optimization model with minimum transaction lots abstract in this paper we consider a multi period fuzzy portfolio optimization problem with minimum transaction lots based on possibility theory we formulate a mean semivariance portfolio selection model with the objectives of maximizing the terminal wealth and minimizing the cumulative risk over the whole investment horizon in the proposed model we take the return risk transaction costs diversification degree cardinality constraint and minimum transaction lots into consideration to reflect investor s aspiration levels for the two objectives a fuzzy decision technique is employed to transform the proposed model into a single objective mixed integer nonlinear programming problem then we design a genetic algorithm for solution finally we give an empirical application in chinese stock markets to demonstrate the idea of our model and the effectiveness of the designed algorithm

menu costs and the neutrality of money a model of endogenous price adjustment under money growth is presented firms follow s s pricing policies and price revisions are imperfectly synchronized in the aggregate price stickiness disappears and money is neutral the connection between firm price adjustment and relative price variability in the presence of monetary growth is also investigated the results contrast with those obtained in models with exogenous fixed timing of price adjustment

cvar models with selective hedging for international asset allocation abstract we develop an integrated simulation and optimization framework for multicurrency asset allocation problems the simulation applies principal component analysis to generate scenarios depicting the discrete joint distributions of uncertain asset returns and exchange rates we then develop and implement models that optimize the conditional value at risk cvar metric the scenario based optimization models encompass alternative hedging strategies including selective hedging that incorporates currency hedging decisions within the portfolio selection problem thus the selective hedging model determines jointly the portfolio composition and the level of currency hedging for each market via forward exchanges we examine empirically the benefits of international diversification and the impact of hedging policies on risk return profiles of portfolios we assess the effectiveness of the scenario generation procedure and the stability of the model s results by means of out of sample simulations we also compare the performance of the cvar model against that of a model that employs the mean absolute deviation mad risk measure we investigate empirically the ex post performance of the models on international portfolios of stock and bond indices using historical market data selective hedging proves to be the superior hedging strategy that improves the risk return profile of portfolios regardless of the risk measurement metric although in static tests the mad and cvar models often select portfolios that trace practically indistinguishable ex ante risk return efficient frontiers in successive applications over several consecutive time periods the cvar model attains superior ex post results in terms of both higher returns and lower volatility

output and welfare effects of inflation with costly price and quantity adjustments there exists by now a burgeoning literature concerned with the consequences of a fixed cost of price adjustment due to this cost a monopolistic firm does not necessarily adjust its price even though the current price deviates from the price that would maximize the firm s current profit as a result the production generally differs from what it would be in the absence of a menu cost with the effect of inflation on the average output and welfare under monopolistic competition being ambiguous and depending in a complicated way on the profit and demand functions 1 however one strong result holds unambiguously for all profit and demand functions at low inflation rates the average output and welfare are above their levels at full price stability where firms charge the static monopoly price 2 the driving force is that discounting makes a firm more concerned with its real profits earlier in a period with a constant nominal price than with its real profits later in the period in fact as the inflation rate approaches zero the firm s initial real price converges to the profit maximizing real price while the terminal real price converges to a smaller real price at low inflation rates therefore a firm s price is most of the time below the price that would maximize the current profit since output and welfare under monopolistic competition are inversely related to price average output and welfare are higher than under full price stability the inevitable conclusion is that the economy benefits from a little bit of inflation a critical assumption underlying this result is that firms can continuously adjust their production to satisfy demand so while the menu cost literature explicitly assumes that there is a small fixed cost incurred at each price adjustment it also implicitly assumes that it is costless to continuously adjust the quantity of output 3 this is however a questionable assumption there is some empirical evidence indicating the existence of a cost of quantity adjustment part of which is fixed in that it does not depend on the size of the adjustment 4 the cost of quantity adjustment stems from the need to rearrange and reorganize the factor inputs for the new level of production and includes managerial time and effort a fixed cost of quantity adjustment rules out any continuous adjustment of the production to satisfy the increasing demand that results from a decreasing real price within a period with a constant nominal price under the reasonable assumption that the menu cost does not exceed the fixed cost of quantity adjustment 5 in an inflationary environment a firm chooses to adjust its nomi

preference programming for robust portfolio modeling and project selection in decision analysis difficulties of obtaining complete information about model parameters make it advisable to seek robust solutions that perform reasonably well across the full range of feasible parameter values in this paper we develop the robust portfolio modeling rpm methodology which extends preference programming methods into portfolio problems where a subset of project proposals are funded in view of multiple evaluation criteria we also develop an algorithm for computing all non dominated portfolios subject to incomplete information about criterion weights and project specific performance levels based on these portfolios we propose a project level index to convey i which projects are robust choices in the sense that they would be recommended even if further information were to be obtained and ii how continued activities in preference elicitation should be focused the rpm methodology is illustrated with an application using real data on road pavement projects

multiple breaks terms of trade shocks and the unit root hypothesis for african per capita real gdp summary this paper presents an investigation of the unit root hypothesis for per capita real gdp series in 46 african countries from maddison 2003 over the period spreading during 1950 and 2001 toward this end we employ highly flexible panel techniques which incorporate multiple mean and slope shifts in the output series our findings are clearly supportive of regime wise trend stationarity in output after 1 allowing for cross dependence and multiple breaks and 2 removing four countries that exert undue influence on the whole panel remarkably our main results hold true for alternative per capita real gdp proxies retrieved from the penn world table 6 2 as well as for different country groups constructed on the basis of the country s participation in regional integration processes interestingly the timing of the breaks broadly coincides with terms of trade shocks associated with large fluctuations in the price of primary commodities based on our results we draw some policy prescriptions that point to the need for managing adequately terms of trade booms and busts to avoid large swings in africa s aggregate output

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

output effects of inflation with fixed price and quantity adjustment costs i introduction there is convincing evidence that fixed costs of price adjustment may be large levy et al 1997 found such costs to be 0 7 of a firm s revenue and zbaracki et al 2004 found them to be 1 22 in the presence of fixed costs of price adjustment a monopolistic firm does not adjust its nominal price continuously with the result that the real price and output generally deviate from their static monopoly level at low inflation rates the average output is higher than the static monopoly output if there is positive discounting danziger 1988 and depends on higher order derivatives of the profit and demand functions if there is no discounting benabou and konieczny 1994 1 most of the literature assumes that only price adjustments are costly while output can be continuously adjusted without cost however bresnahan and ramey 1994 document that there may be large fixed costs of quantity adjustments relatedly many publications show that adjusting labor and capital inputs involves significant fixed costs 2 such costs may derive from loss of organizational capital baily et al 2001 jovanovic and rousseau 2001 as well as from job protection rules severance pay and legal and administrative complications in a framework with both price and quantity adjustment costs andersen 1995 and andersen and toulemonde 2004 demonstrate that only intermediate size shock but not large or small shocks may affect output for a constant inflation rate danziger 2001 shows that a firm s permanent production decreases with inflation at low inflation rates if discounting is positive and danziger and kreiner 2002 that output capacity decreases with inflation if the elasticity of demand is constant and there is no discounting see also danziger 2003 the purpose of this article is to provide a simple general characterization of the output effects of a constant inflation rate if both price and quantity adjustments involve fixed costs it is assumed that quantity adjustments are at least as costly as price adjustments which implies that a firm s production is held constant at a permanent level 3 each firm then keeps its nominal price unchanged in periods of equal length and the nominal price is adjusted so that the initial real price is the same in each period thus a firm s optimal strategy consists of the initial real price the duration of the periods with unchanged nominal price and the permanent level of production the article shows that in the absence of discounting the effect of inflation on the aggregate production depends on how fast firms marginal real revenue decreases with demand and that this effect is fully determined by the elasticity of the marginal real revenue with respect to demand thus aggregate production decreases with inflation if the elasticity of the marginal real revenue always exceeds minus unity increases with inflation if the elasticity of the marginal real revenue is always less than minus unity and is invariant to inflation if the elasticity of the marginal real revenue always equals minus unity several studies have found that the comovement between output and prices is typically negative in the long run cooley and ohanian 1991 den haan 2000 den haan and sumner 2004 fiorito and kollintzas 1994 within the framework of the present model the negative comovement indicates that the empirically relevant situation is when the elasticity of the marginal real revenue always exceeds minus unity this will be the case among others if demand functions exhibit a constant price elasticity less than minus unity as assumed in danziger and kreiner 2002 ii the model consider an economy with a unit continuum of identical consumers and a unit continuum of monopolistic firms producing differentiated perishable products each firm and its product are indexed by i which is uniformly distributed on 0 1

a letter to the editor on wage bargaining abstract the rubinstein perfect information alternating offers bargaining model is problematic when applied to wage negotiations a strike or any other industrial action is not an automatic consequence of a delay in reaching an agreement because production can continue normally also when negotiations take place this paper extends the rubinstein model to incorporate the choice of calling a strike and it is shown that in this model there is no longer a unique subgame perfect equilibrium and that strikes with a length in real time can occur in equilibrium

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

exchange rate uncertainty forward contracts and international portfolio selection in this paper ex ante efficient portfolio selection strategies are developed to realize potential gains from international diversification under flexible exchange rates it is shown that exchange rate uncertainty is a largely nondiversiflable factor adversely affecting the performance of international portfolios therefore it is essential to effectively control exchange rate volatility for that purpose two methods of exchange risk reduction are simultaneously employed multicurrency diversification and hedging via forward exchange contracts the empirical findings show that international portfolio selection strategies designed to control both estimation and exchange risks almost consistently outperform the u s domestic portfolio in out of sample periods since grubel 11 applied modern portfolio theory mpt to international investment various authors such as levy and sarnat 17 solnik 20 and lessard 16 have examined the gains from international diversification of investment portfolios for the purpose of establishing the gains from international diversification these studies constructed international portfolios using historical risk and return data from a period of fixed or relatively stable exchange rates and showed that internationally diversified portfolios dominated purely domestic portfolios in terms of mean variance efficiency from the standpoint of today s investors however the previous studies fail to offer operational guidance for international diversification for two important reasons first it is now questionable whether the past findings are still relevant under the current flexible exchange rate regime second by being ex post in nature the past studies ignored the issue of estimation risk or parameter uncertainty and therefore may have overstated the realizable portion of the potential gains from international diversification fluctuating exchange rates are likely to mitigate the potential gains from international diversification by making investment in foreign securities more risky as will be shown later a fluctuating exchange rate contributes to the risk of foreign investment not only through its own variance but also through its positive covariances with the local stock market returns during our sample period of 1980 through 1985 for example exchange rate volatility is found to account for about fifty percent of the volatility of dollar returns from investment in the stock markets of such major countries as germany japan and the u k furthermore the exchange rate changes vis a vis the u s dollar are found to be

contract duration and investment incentives evidence from land tenancy agreements this paper analyzes the empirical determinants of contract length a key and yet neglected dimension of contractual structure i estimate contract length and contract type jointly using original data on tenancy agreements signed between 1870 and 1880 in the district of siracusa italy the findings indicate that the choice of contract length is driven by the need to provide incentives for nonobservable investment taking into account transaction costs and imperfections in the credit markets that make incentive provision costly the results also illustrate that because both length and the compensation scheme are used to provide incentives within the same contract joint analysis is important for a correct interpretation of the evidence jel d82 o12 q15

numerical approximations of optimal portfolios in mispriced asymmetric levy markets abstract we present numerical approximations of optimal portfolios in mispriced levy markets under asymmetric information for informed and uninformed investors having logarithmic preference we apply our numerical scheme to kou 2002 jump diffusion markets by deriving analytic formulas for the first two derivatives of the underlying portfolio objective function which depend only on the levy measure of the jump generating process optimal portfolios are then simulated using the box muller algorithm newton s method and incomplete beta functions convergence dynamics and trajectories of sample paths of optimal portfolios for both investors are presented at different levels of information asymmetry mispricing horizon asymmetry in the kou density jump intensity volatility mean reversion speed and sharpe ratios we also apply the proposed newton s algorithm to compute optimal portfolios for investors in variance gamma markets via instantaneous centralized moments of returns

contract adjustment under uncertainty abstract consider trade in continuous time between two players the gains from trade are divided according to a contract and at each point in time either player may unilaterally induce a costly adjustment of the contract players payoffs from trade under the contract as well as from trade under an adjusted contract are exogenous and stochastic we consider players choice of whether and when to adjust the contract payment we show that there exists a nash equilibrium in thresholds where each player adjusts the contract whenever the contract payment relative to the outcome of an adjustment passes the threshold there is strategic substitutability in the choice of thresholds so that if one player becomes more active by choosing a threshold closer to unity the other player becomes more passive

terms of trade shocks in africa are they short lived or long lived abstract this paper examines the persistence of shocks to the terms of trade using annual data on 42 sub saharan african countries for the period 1960 96 instead of using unit root tests to distinguish between stationary and random walk processes for the terms of trade this paper characterizes the persistence of shocks using point and interval estimates of the half lives of terms of trade shocks using median unbiased mu estimation techniques that remove the downward bias of standard least squares ls estimators we find that the cross country average of the half lives of terms of trade shocks is about 6 years it is also found that the estimated persistence of african terms of trade shocks varies widely for about one half of the countries their half lives are short lived less than 4 years while for one third of the countries their half lives are long lived permanent the majority of african countries are found to have terms of trade that typically experience finitely persistent transitory shocks which is consistent with the reversion of terms of trade to their long run trends

incorporating asymmetric distributional information in robust value at risk optimization value at risk var is one of the most widely accepted risk measures in the financial and insurance industries yet efficient optimization of var remains a very difficult problem we propose a computationally tractable approximation method for minimizing the var of a portfolio based on robust optimization techniques the method results in the optimization of a modified var measure asymmetry robust var arvar that takes into consideration asymmetries in the distributions of returns and is coherent which makes it desirable from a financial theory perspective we show that arvar approximates the conditional var of the portfolio as well numerical experiments with simulated and real market data indicate that the proposed approach results in lower realized portfolio var better efficient frontier and lower maximum realized portfolio loss than alternative approaches for quantile based portfolio risk minimization

currency hedging for international portfolios this paper examines the benefits from currency hedging both for speculative and risk minimization motives in international bond and equity portfolios the riskreturn performances of globally diversified portfolios are compared with and without forward contracts over the period 1974 to 1990 inclusion of forward contracts results in statistically significant improvements in the performance of unconditional portfolios containing bonds conditional strategies are also implemented both in sample and out of sample and are shown to both significantly improve the risk return tradeoff of global portfolios and to outperform unconditional hedging strategies whether international portfolios should be hedged against currency risks is the subject of an active debate the theoretical side of the debate has been closely associated with two strands in the academic literature international asset pricing and optimal hedging in the futures markets in the international asset pricing model iapm of solnik 1974 optimal portfolios contain positions in forward contracts or equivalently foreign currency denominated bills these positions which can differ from the positions in foreign stocks have since been termed hedges black 1990 shows that under additional assumptions the hedge ratios should be identical for all investors regardless of their nationality universality and that investors should never fully hedge their foreign currency exposures similarly theoretical models from the futures literature produce demands for hedging instruments that contain both speculative and hedging components the empirical issue unanswered so far is whether adding forward contracts to international portfolios significantly improves the risk return profile of global investments empirical research has barely begun to respond to the challenges of theoretical models there exists little empirical evidence on either the relevance of black s universal hedge ratios or the optimality of hedge ratios less than one instead researchers have concentrated on the benefits of fully hedging exchange risk for example eun and resnick 1988 indicate that stock portfolios perform better when fully hedged but offer no statistical tests

integrated portfolio management with options in this paper we examine the problem of managing portfolios consisting of both stocks and options for the simultaneous optimization of stock and option positions we base our analysis on the generally accepted mean variance framework first we analyze the effects of options on the mean variance efficient frontier if they are considered as separate investment alternatives due to the resulting asymmetric portfolio return distribution mean variance analysis will be not sufficient to identify optimal optioned portfolios additional investor preferences which are expressed in terms of shortfall constraints allow a more detailed portfolio specification under a mean variance and shortfall preference structure we then derive optioned portfolios with a maximum expected return to circumvent the technical optimization problems arising from stochastic constraints we use an approximation of the return distribution and develop economically meaningful conditions under which the complex optimization problem can be transformed into a linear problem being comparably easy to solve empirical results based on both empirical market data and monte carlo simulations illustrate the portfolio optimization procedure with options

a currency preferential approach to international equity investment we propose a timex strategy for reducing the foreign exchange risk associated with international equity investment pertaining to countries with currencies correctly or undervalued by the standard of ppp the performance of timex is examined from the perspectives of eight developed nations with long histories of free floating currencies based on the data from 1986 q1 to 2014 q4 we find unambiguous evidence for the superior performance of timex in the foreign exchange market compared with the passive diversification strategy and the morgan stanley capital international msci world index timex offers higher total returns and risk adjusted total returns when rebalanced every 6 or 12 months for investors based in all eight countries under study when rebalanced at a 3 year interval timex outperforms the passive diversification and the msci world index for five and all eight countries respectively

wage bargaining and nominal rigidities abstract delays in wage negotiations do not necessarily mean work stoppage production can continue under the terms of the old contract while the parties are bargaining holdout this holdout option is included in a strategic bargaining game in addition to strike and lock out threats integrating the bargaining model in a standard macroeconomic framework it turns out that holdout threats will prevail under certain circumstances in this case wages will be rigid in nominal terms so that an increase in aggregate nominal demand increases aggregate output

striking for a bargain between two completely informed agents this paper models the wage contract negotiation procedure between a union and a firm as a sequential bargaining process in which the union must decide in each period whether or not to strike for the duration of that period we show that there exist subgame perfect equilibria in which the union engages in several periods of strikes prior to reaching a final agreement although both parties are completely rational and fully informed this has implications for other inefficient phenomena such as tariff wars debt negotiations and wars in general we characterize the set of equilibria show that strikes can occur in real time and discuss extensions of the model such as lockouts and the possibility of multiple recontracting opportunities copyright 1991 by american economic association

an expected regret minimization portfolio selection model abstract fuzzy portfolio selection has been widely studied within the framework of the credibility theory however all existing models provide only concentrated investment solutions which contradicts the risk diversification concept in the classical portfolio selection theory in this paper we propose an expected regret minimization model which minimizes the expected value of the distance between the maximum return and the obtained return associated with each portfolio we prove that our model is advantageous for obtaining distributive investment and reducing investor regret the effectiveness of the model is demonstrated by using an example of a portfolio selection problem comprising ten securities in the shanghai stock exchange 180 index

ratification requirement and bargaining power when a large group of people is affected by a bargaining outcome practical reasons often require that the group be represented by an agent in the bargaining this paper addresses the issue of how the group ensures that the agent reaches an agreement that satisfies the group the authors show that by adopting a super majority ratification rule the group may improve its bargaining position and obtain a larger share of the bargaining surplus however a super majority ratification rule also involves the risk that a beneficial agreement is rejected by a minority of the group copyright 1997 by economics department of the university of pennsylvania and the osaka university institute of social and economic research association

african terms of trade and the commodity terms of trade close cousins or distant relatives this paper examines whether there is a relationship between the commodity terms of trade the price of primary commodities relative to the price of manufactures and the net barter terms of trade of 42 sub saharan african countries for most countries there is little evidence of a stable long run relationship between the two terms of trade series accordingly the practice in the literature of proxying for movements in any given country s terms of trade by using an aggregate index of relative commodity prices is inappropriate and is likely to engender misleading policy conclusions

aggregation and optimization with state dependent pricing the literature on the aggregation of s s policies has ignored the impact of aggregate behavior on the individual s optimization problem in the case of pricing the feedback effects are clear not only do pricing strategies determine the evolution of the price level but the evolution of the price level also influences the optimal pricing strategies in this paper we provide a consistent treatment of aggregation and optimization we use this model to analyze three issues in the menu cost pricing literature the relationship between strategic complementarity and the real effects of money the relationship between the variance of the money supply and the correlation between money and output and the relationship between the cost of price adjustment and the size of price adjustment questions concerning the dynamics of aggregate variables such as prices employment investment and consumption represent the core of business cycle analysis one striking feature of these variables is the radical difference between properties of these aggregates and the nature of the individual behavior that underlies them the behavior of a firm s prices investment and employment and the behavior of an individual s consumption all involve frictional elements that lead to discrete adjustment at the microeconomic level heterogeneity among individuals however tends to smooth the behavior of the corresponding aggregates in recent years a large body of research has developed to examine the manner in which microeconomic frictions influence aggregate dynamics one of the centerpieces of this research has been the s s model developed by arrow harris and marschak 1951 the key element of this model is the state dependence of individual decisions agents act when a state variable crosses some critical threshold which balances the cost and benefits of adjustment the aggregate implications of this form of microeconomic behavior have been analyzed by blinder 1981 caplin 1985 and mosser 1991 in the context of inventory dynamics by caplin and spulber 1987 caballero and engel 1991 1993 and caplin and leahy 1991 in the context of prices and by bertola and caballero 1990 caballero 1993 and eberly 1994 in the context of con sumer durables one of the most limiting aspects of these models is that they focus exclusively on the impact that microeconomic inertia has on aggregate dynamics they 1we would like to thank michael harrison loannis karatzas john leahy sr andreu mas colell a co editor and four anonymous referees for helpful discussions and comments and the national science foundation and the sloan foundation for financial support

primary commodity prices manufactured goods prices and the terms of trade of developing countries what the long run shows the authors revisit in this article the empirical foundation of the alleged secular decline in the prices of primary commodities relative to those of manufactures they use a newly constructed index of commodity prices and two modified indexes of manufactured good prices and find that from 1900 to 1986 the relative prices of all primary commodities fell on trend by 0 5 percent a year and those of nonfuel primary commodities by 0 6 percent a year they thus confirm the sign but not the magnitude of the trend implicit in the work of prebisch but even the more limited secular decline shown by their relative price indexes may be magnified by an incomplete account of quality improvements in manufactures they then show that the evolution of terms of trade of nonfuel primary commodities is not the same as that of the net barter terms of trade of non oil exporting developing countries finally they find that despite the decline that has probably occurred during the current century in the terms of trade of nonfuel primary commodities the purchasing power of total exports of these products has increased considerably similarly the fall that may have occurred after world war ii in the net barter terms of trade of developing countries seems to have been more than compensated for by the steady improvement in their income terms of trade

international portfolio management with affine policies abstract while dynamic decision making has traditionally been represented as scenario trees these may become severely intractable and difficult to compute with an increasing number of time periods we present an alternative tractable approach to multiperiod international portfolio optimization based on an affine dependence between the decision variables and the past returns because local asset and currency returns are modeled separately the original model is non linear and non convex with the aid of robust optimization techniques however we develop a tractable semidefinite programming formulation of our model where the uncertain returns are contained in an ellipsoidal uncertainty set we add to our formulation the minimization of the worst case value at risk and show the close relationship with robust optimization numerical results demonstrate the potential gains from considering a dynamic multiperiod setting relative to a single stage approach

robust strategies for facility location under uncertainty abstract this paper considers a stochastic facility location problem in which multiple capacitated facilities serve customers with a single product and a stockout probabilistic requirement is stated as a chance constraint customer demand is assumed to be uncertain and to follow either a normal or an ambiguous distribution we study robust approximations to the problem in order to incorporate information about the random demand distribution in the best possible computationally tractable way we also discuss how a decision maker s risk preferences can be incorporated in the problem through robust optimization finally we present numerical experiments that illustrate the performance of the different robust formulations robust optimization strategies for facility location appear to have better worst case performance than nonrobust strategies they also outperform nonrobust strategies in terms of realized average total cost when the actual demand distributions have higher expected values than the expected values used as input to the optimization models

robust tracking error portfolio selection with worst case downside risk measures abstract this paper proposes downside risk measure models in portfolio selection that captures uncertainties both in distribution and in parameters the worst case distribution with given information on the mean value and the covariance matrix is used together with ellipsoidal and polytopic uncertainty sets to build up this type of downside risk model as an application of the models the tracking error portfolio selection problem is considered by lifting the vector variables to positive semidefinite matrix variables we obtain semidefinite programming formulations of the robust tracking portfolio models numerical results are presented in tracking sse50 of the shanghai stock exchange compared with the tracking error variance portfolio model and the equally weighted strategy the proposed models are more stable have better accumulated wealth and have much better sharpe ratio in the investment period for the majority of observed instances

international portfolio diversification with estimation risk international portfolio diversification has long been advocated as a way of enhancing average returns while reducing portfolio risk for the investor who considers diversifying into foreign securities this proposition however relies on the assumption that the required inputs to the classical mean variance analysis are known with certainty typically expected returns variances and covariances are simply replaced by their ex post sample values and the optimal portfolio is derived without mentioning the uncertainty inherent in these parameter values but the rational investor should take this uncertainty into account when forming expectations and probably will consider estimators that are less subject to estimation error than the classical sample mean this paper investigates alternative estimators of expected returns and their implications for the alleged gains from diversification an important observation is the crucial influence that errors in estimating expected returns have on portfolio analysis a closer examiprevious studies of international portfolio diversification have relied on ex post meanvariance analysis without considering the problem of estimation risk typically past averages are substituted for expected returns and no allowance is made for the uncertainty inherent in these parameter values first i demonstrate the shortcomings of such an approach and second i investigate another method of estimating expected returns initially proposed by stein by shrinking the sample averages toward a common mean i find that the out of sample performance of the optimal portfolio is substantially increased one of the implications of this method is that the classical conclusions vastly overestimate the possible gains in average returns instead benefits from diversification are more likely to accrue from a reduction in risk this paper draws on part of my dissertation at the university of chicago i am grateful to arnold zellner michael mussa george constantinides and especially john bilson for useful discussions and comments numerous improvements were also suggested by the referee this research received the generous financial support of the college interuniversitaire d etudes doctorales dans les sciences du management

optimum pricing policy under stochastic inflation we describe aggregate inflation as a stochastic process in which the rate of change of the price level can be positive or zero where the times spent in each state are of random duration this class of processes includes two state markov chains and renewal processes as special cases it is shown that the optimal pricing policy of a monopolistic firm with non convex costs of price adjustment is s s in its real price i e its nominal price relative to the price level a basic certainty equivalence result is proved i e the firm behaves as if it faces a certain and fixed rate of inflation higher than the actual expected rate the difference between the two rates being a risk premium which depends on the real interest rate and the parameters of the stochastic process one can thus apply previous results from the case of certainty sheshinski and weiss review of economic studies 1977 to obtain comparative static results in particular one finds that an increase in the variance of expected inflation leads firms to choose a pricing policy with larger amplitude in real price the paper also addresses the question of consistency in firms expectations when the price level is determined by the firms actions in this paper we consider pricing policies of individual firms in an inflationary environment each firm expects the general price level to increase and must determine the rate of increase of its own price it is assumed that the firm incurs an adjustment cost when it changes its nominal price consequently firms choose to change prices occasionally rather than continuously

equilibrium exchange rate hedging we assume a world like the one that gives the capital asset pricing model but with many goods and many countries we assume that investors in a given country have homothetic utility functions with the same weights and a currency that has a sure endof period value using a price index with those weights siegel s paradox derived from jensen s inequality makes investors want a positive amount of exchange risk when average risk tolerance is the same across countries every investor will hold the same mix of market risk through the world market portfolio of all assets and exchange risk in a diversified basket of foreign currencies in fact the ratio of exchange risk to market risk is equal to the average investor s risk tolerance we can write the ratio of exchange risk to market risk and the fraction of the market s exchange risk that investors hedge as depending on an average of world market risk premia an average of world market volatilities and an average of exchange rate volatilities the weights in these averages are the same as the weights of the different countries in the currency basket given these averages the ratio and the fraction hedged will not depend directly on exchange rate means or covariances in equilibrium we can use the ratio of exchange risk to market risk to measure average risk tolerance in this model risk tolerance is observable

worst case value at risk and robust portfolio optimization a conic programming approach classical formulations of the portfolio optimization problem such as mean variance or value at risk var approaches can result in a portfolio extremely sensitive to errors in the data such as mean and covariance matrix of the returns in this paper we propose a way to alleviate this problem in a tractable manner we assume that the distribution of returns is partially known in the sense that onlybounds on the mean and covariance matrix are available we define the worst case value at risk as the largest var attainable given the partial information on the returns distribution we consider the problem of computing and optimizing the worst case var and we show that these problems can be cast as semidefinite programs we extend our approach to various other partial information on the distribution including uncertainty in factor models support constraints and relative entropy information

robust and pareto optimality of insurance contracts the optimal insurance problem represents a fast growing topic that explains the most efficient contract that an insurance player may get the classical problem investigates the ideal contract under the assumption that the underlying risk distribution is known i e by ignoring the parameter and model risks taking these sources of risk into account the decision maker aims to identify a robust optimal contract that is not sensitive to the chosen risk distribution we focus on value at risk var and conditional value at risk cvar based decisions but further extensions for other risk measures are easily possible the worst case scenario and worst case regret robust models are discussed in this paper which have been already used in robust optimisation literature related to the investment portfolio problem closed form solutions are obtained for the var worst case scenario case while linear programming lp formulations are provided for all other cases a caveat of robust optimisation is that the optimal solution may not be unique and therefore it may not be economically acceptable i e pareto optimal this issue is numerically addressed and simple numerical methods are found for constructing insurance contracts that are pareto and robust optimal our numerical illustrations show weak evidence in favour of our robust solutions for var decisions while our robust methods are clearly preferred for cvar based decisions

state dependent pricing and the general equilibrium dynamics of money and output economists have long suggested that nominal product prices are changed infrequently because of fixed costs in such a setting optimal price adjustment should depend on the state of the economy yet while widely discussed statedependent pricing has proved difficult to incorporate into macroeconomic models this paper develops a new tractable theoretical state dependent pricing framework we use it to study how optimal pricing depends on the persistence of monetary shocks the elasticities of labor supply and goods demand and the interest sensitivity of money demand

a discontinuous mispricing model under asymmetric information we study a discontinuous mispricing model of a risky asset under asymmetric information where jumps in the asset price and mispricing are modelled by levy processes by contracting the filtration of the informed investor we obtain optimal portfolios and maximum expected utilities for the informed and uninformed investors we also discuss their asymptotic properties which can be estimated using the instantaneous centralized moments of return we find that optimal and asymptotic utilities are increased due to jumps in mispricing for the uninformed investor but the informed investor still has excess utility provided there is not too little or too much mispricing

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

effects of higher order moments on the newsvendor problem abstract in this paper we propose a stochastic programming model for the well known single period newsvendor problem by adopting the conditional value at risk cvar as the risk metric in the objective function the demand uncertainty is modeled in terms of discrete scenarios that reflect the empirical distributions implied by market demand data our numerical results demonstrate that the higher order moments skewness and kurtosis of demand have obvious effects on the newsvendor problem and the stochastic programming framework provides a flexible and effective decision support tool for the newsvendor problem

is complete hedging optimal for international bond portfolios over the 1980s however non u s investors could have lowered their international portfolios risks by taking on some currency exposure for these investors the benefits of diversification across currencies more than offset the cost of the currencies volatilities evidently the free lunch argument misses something and investors should be concerned that the missing link might change across countries or over time

risk analysis with contractual default does covenant breach matter abstract mergers and acquisitions m a private equity and leveraged buyouts securitization and project finance are characterized by the presence of contractual clauses covenants these covenants trigger the technical default of the borrower even in the absence of insolvency therefore borrowers may default on loans even when they have sufficient available cash to repay outstanding debt this condition is not captured by the net present value npv distribution obtained through a standard monte carlo simulation in this paper we present a methodology for including the consequences of covenant breach in a monte carlo simulation extending traditional risk analysis in investment planning we introduce a conceptual framework for modeling technical and material breaches from the standpoint of both lenders and shareholders we apply this framework to a real case study concerning the project financing of a 64 million euro biomass power plant the simulation is carried out on the actual model developed by the financial advisor of the project and made available to the authors results show that both technical and material breaches have a statistically significant impact on the net present value distribution and this impact is more relevant when leverage and cost of debt increase