transaction costs and efficiency of portfolio strategies abstract some recent results for frictionless economies show that popular dynamic portfolio strategies such as stop loss and lock in are inefficient i e for each of these strategies there exists an alternative portfolio strategy that gives the same final payoff distribution at lower initial costs however the alternative strategies require considerably more active trading than the simple strategies the results rely heavily on the assumption of no transaction costs under this assumption the initial investment required is a linear function of the prices of the contingent claims that build the final payoff distribution in this paper we demonstrate that even for modest levels of transaction costs the efficient strategies are more costly than the simple strategies i e a strategy that replicates the final payoff distribution of an efficient strategy is excessively costly due to the transaction costs and the heavy trading involved since the initial investment is no longer a linear function of the contingent claims the optimization problems to find the most efficient strategy are complicated combinatorial optimization problems which can only be solved for trees with a small number of steps in a world without transaction costs options are redundant instruments since all payoff distributions can be replicated by trading in stocks and bonds in the second half of this paper we show that the use of options in a world with transaction costs enables investors to realize final value distributions at lower initial costs than would be possible with trades in stocks an bonds only hence although in theory options do not give rise to other portfolio strategies they do in a more restrictive setting with transaction costs

earnings skewness and analyst forecast bias abstract we argue that if analysts objective is to provide the most accurate forecast by minimizing the mean absolute forecast error then the optimal forecast is the median instead of the mean earnings forecast bias is observed when the median is different from the mean in a skewed earnings distribution thus part of the observed analyst forecast bias could be a result of analysts efforts to improve forecast accuracy when the earnings distribution is skewed we find that earnings skewness is significantly related to analyst forecast bias we also provide evidence that the market adjusts for part of the skewness induced bias

how valuable is patent protection estimates by technology field i present evidence on the private value of patent rights in france for different technology fields and nationalities of ownership using nonparametric techniques and a parametric model of patent renewal i find that the distribution of the value of patent rights is highly skewed that patent protection is a significant but not the major source of private returns to r d and that these characteristics vary across technology fields i compute the r d cash subsidy that is equivalent to the value of patent rights measure the variations in value of time technology fields and nationalities and show that these differences are correlated with patent grant rates

the risk in hedge fund strategies theory and evidence from trend followers hedge fund strategies typically generate option like returns linear factor models using benchmark asset indices have difficulty explaining them following the suggestions in glosten and jagannathan 1994 this article shows how to model hedge fund returns by focusing on the popular trend following strategy we use lookback straddles to model trend following strategies and show that they can explain trend following funds returns better than standard asset indices though standard straddles lead to similar empirical results lookback straddles are theoretically closer to the concept of trend following our model should be useful in the design of performance benchmarks for trend following funds

regulating a monopolist with unknown demand and cost functions we consider the design of regulatory policy when the regulator is imperfectly informed about both the firm s cost function and the demand function it faces to some extent the optimal policy here is the natural combination of the optimal policies when there is uncertainty only about either demand or cost important qualitative differences also exist however for example it may be optimal to set prices below marginal cost and the pricing authority delegated to the firm may be more limited when there is uncertainty about both cost and demand

the economics of invention incentives patents prizes and research contracts though public intervention in the market for research is virtually universal economists have paid surprisingly little attention to the choice of the form of research incentive in a given market structure many studies concentrate on patents but any assumption of their superiority over other incentives has been founded on intuition rather than on formal analysis in this paper i analyze the choice between three of the most common alternative means of public intervention in the research market namely patents prizes and direct contracting for research services i show why and under what conditions any one of the three may be preferred by a social welfare maximizing administrator in a competitive economy using a model that for the first time pays explicit attention to differences in the informational roles of each of these alternatives in the extensive literature on the economics of patents see arnold plant 1934 fritz machlup 1958 charles taylor and z a silberston 1973 morton kamien and nancy schwartz 1975 and f m scherer 1977 for valuable surveys formal analysis weighs the benefits of patents as a solution to the market failure associated with the inappropriability of knowledge against the welfare cost due to the restriction on the use of the knowledge generated and this tradeoff is optimized by patent life adjustment in william nordhaus 1969 scant analytical attention is paid to alternative incentive mechanisms an exception is ben yu 1981 who considers the role of prior contracting for inventions but as many writers for example dan usher 1964 yoram barzel 1968 joseph stiglitz 1969 carole kitti 1973 glenn loury 1979 partha dasgupta and stiglitz 1980a have pointed out in various contexts the incentive offered by an unlimited patent to competitive researchers may be excessive due to the common pool problem discussed further in section i below if the patent administrator and researchers share the same information as implicitly assumed in previous models then the patent life limitation can be adjusted to provide the optimal patent incentive given the common pool problem but in all such models patents would not be chosen in a fully optimized fiscal system researchers and the administrator are assumed to have identical information about the shadow price of potential inventions a patent is just a means of turning this shadow price into a monetary reward but monetary compensation can instead be offered directly to researchers by the state assuming that patent revenues incur a higher deadweight loss than an equivalent amount of public funds financed by less distortionary means for example a minimally efficient tax system appropriate prizes or government contracts are socially preferable to patents with optimal lives if the patent is ever to be the optimal incentive mechanism for research it must possess advantages not captured in existing models informal discussions of patents emphasize their informational role to include the latter as a justification for decentralized invention incentives i incorporate an ex ante imbalance of information about costs and benefits of research in the model presented in section ii but this alone is not quite enough it is further necessary to specify that the terms of the award must be fixed before department of economics economic growth center box 1987 yale station yale university new haven ct 06520 i thank with the usual caveat marguerite alejandro wright cindy arfken martin baily nuong brennan steven englander robert evenson richard levin richard nelson susan rose ackerman denis wright and two referees for assistance of various kinds

shared patent rights and technological progress we study how to reward innovators who build on one another rewards come in the form of patents because patent rights are scarce the optimal allocation involves sharing more than one innovator s patent is in force at a given time we interpret such allocations as patents that infringe one another as licensing through an ever growing patent pool and as randomization through litigation we contrast the rate of technological progress under the optimal allocation with the outcome if sharing is prohibitively costly avoiding sharing initially slows progress and leads to a more variable rate of technological progress

higher risk lower returns what hedge fund investors really earn abstract the returns of hedge fund investors depend not only on the returns of the funds they hold but also on the timing and magnitude of their capital flows in and out of these funds we use dollar weighted returns a form of internal rate of return irr to assess the properties of actual investor returns on hedge funds and compare them to buy and hold fund returns our main finding is that annualized dollar weighted returns are on the magnitude of 3 to 7 lower than corresponding buy and hold fund returns using factor models of risk and the estimated dollar weighted performance gap we find that the real alpha of hedge fund investors is close to zero in absolute terms dollar weighted returns are reliably lower than the return on the standard poor s s p 500 index and are only marginally higher than the risk free rate as of the end of 2008 the combined impression from these results is that the return experience of hedge fund investors is much worse than previously thought

openness open source and the veil of ignorance author s scotchmer suzanne abstract the open source movement evolved in the one industrial context where openness is not required by intellectual property law 1 nevertheless openness itself cannot be the driving force behind the open source movement this is because openness can be achieved in many ways other than the gpl for example with proprietary licenses or licenses that are even more permissive than the gpl such as the bsd license early commentators explained this new development model by focussing on the motives of the programmer such as to demonstrate skills see the survey by stephen m maurer and suzanne scotchmer 2006 but firms also participate in open source collaborations sometimes contributing significant resources joachim henkel 2006 dirk riehle 2009 doing so can be profitable even if the contributors are rivals in the market the quality improvements or cost reductions provided by a rival s open source contributions may outweigh the deleterious effect of empowering the rival to be a better competitor

inefficient dynamic portfolio strategies or how to throw away a million dollars in the stock market a number of portfolio strategies followed by practitioners are dominated because they are incompletely diversified over time the payoff distribution pricing model is used to compute the cost of following undiversified strategies simple numerical examples illustrate the technique and computer generated examples provide realistic estimates of the cost of some typical policies using reasonable parameter values the cost can be substantial and should not be ignored by practitioners a section on generalizations shows how to extend the analysis to term structure models and other general models of returns this abstract was borrowed from another version of this item

patent protection in the shadow of infringement simulation estimations of patent value empirical estimates of the private value of patent protection are derived for four technology areas computers textiles combustion engines and pharmaceuticals using new patent data for west germany 1953 1988 patentees must pay renewal fees to keep their patents in force as well as legal expenses in order to enforce them a dynamic stochastic discrete choice model of optimal renewal decisions is developed incorporating both learning and depreciation as well as the potential need to prosecute infringement the evolution of the distribution of returns over the life of a group of patents is calculated for each technology using a minimum distance simulation estimator results indicate that the aggregate value of protection generated per year is on the order of 10 of related r d expenditure

on dynamic investment strategies abstract this paper presents a new approach for analyzing dynamic investment strategies previous studies have obtained explicit results by restricting utility functions to a few specific forms not surprisingly the resultant dynamic strategies have exhibited a very limited range of behavior in contrast we examine what might be called the inverse problem given any specific dynamic strategy can we characterize the results of following it through time more precisely can we determine whether it is self financing yields path independent returns and is consistent with optimal behavior for some expected utility maximizing investor we provide necessary and sufficient conditions for a dynamic strategy to satisfy each of these properties

distributional analysis of portfolio choice trading in a market is compared with receiving some particular consu mption bundle given increasing state independent preferences and complete markets the analysis focuses on the distribution price of t he particular bundle the distributional price is the price of the ch eapest utility equivalent bundle sold in the market the distribution al price is determined by the distribution functions of the outside b undle and the state price density simple portfolio performance measu res illustrate the value of the approach unlike capm based measures these measures are valid even when superior information is the sourc e of superior performance copyright 1988 by the university of chicago

an analysis of the efficiency of the oil refining industry in the oecd countries abstract this study investigated the efficiency of the oil refining industry using the two stage method of markowitz portfolio optimization theory and panel data analysis of about 30 oecd countries from 2005 to 2016 which is a new methodology for measuring the efficiency of the oil industry the oil refining industry s efficiency is derived from the prices of petroleum products naphtha gasoline kerosene diesel and fuel oil using the portfolio theory the panel data was constructed using the following dependent variables the crude oil production efficiency energy consumption renewable energy consumption and r d investment using the panel data analysis empirical analyzes are conducted on how the efficiency of the oil refining industry is affected by explanatory variables the results show that crude oil production and energy use in oecd countries have a negative effect on the efficiency of the oil refining industry and consumption of renewable energy and r d investment have a positive effect contrary to conventional perception the petroleum industry can coexist with the renewable energy industry for sustainable development

on the short term predictability of exchange rates a bvar time varying parameters approach abstract in this paper we propose a bayesian vector autoregressive model with time varying parameters bvar tvp to examine the short term predictability of exchange rates an important contribution of the paper is the application of the bvar tvp model for the first time to daily data using information from financial markets another contribution is the production of forecasts in real time at the very short horizon of one trading day ahead typically used by traders and investors in financial markets we employ financial criteria and recently developed statistical tests to assess the exchange rate predictability we find that the bvar tvp model outperforms the random walk for all exchange rates these forecast gains are due primarily to the time variation of coefficients and secondly to information from other financial markets it is shown that international investors could have made statistically significant excess profits if they had followed an inter day trading strategy based on the buy sell signals generated by the model s one day ahead exchange rate forecasts even after allowing for transaction costs and risk factors

optimal consumption and portfolio policies when asset prices follow a diffusion process abstract we consider a consumption portfolio problem in continuous time under uncertainty a martingale technique is employed to characterize optimal consumption portfolio policies when there exist nonnegativity constraints on consumption and on final wealth we also provide a way to compute and verify optimal policies our verification theorem for optimal policies involves a linear partial differential equation unlike the nonlinear partial differential equation of dynamic programming the relationship between our approach and dynamic programming is discussed we demonstrate our technique by explicitly computing optimal policies in a series of examples in particular we solve the optimal consumption portfolio problem for hyperbolic absolute risk aversion utility functions when the asset prices follow a geometric brownian motion the optimal policies in this case are no longer linear when nonnegativity constraints on consumption and on final wealth are included by these examples one can see that our approach is much easier than the dynamic programming approach

runner up patents is monopoly inevitable exclusive patents sacrifice product competition to provide firms incentives to innovate we characterize an alternative mechanism whereby later inventors are allowed to share the patent if they discover within a certain time period of the first inventor these runner up patents increase social welfare under very general conditions furthermore we show that the time window during which later inventors can share the patent should become a new policy tool at the disposal of the designer this instrument will be used in a socially optimal mix with the breadth and length of the patent and could allow sorting between more or less efficient firms

on the optimality of the patent renewal system the patent system is mainly a renewal system the patent life is chosen by the patentee in return for fees i ask whether such a system can be justified by asymmetric information on costs and benefits of research in such a model i show that renewal mechanisms possibly with subsidies are equivalent to direct revelation mechanisms and therefore cannot be improved on regardless of the objective function under plausible circumstances patents should have a uniform life rather than varying in length as typically occurs under a renewal system

sufficient conditions for expected utility to imply drawdown based performance rankings the least restrictive sufficient condition for expected utility to imply sharpe ratio rankings is the location and scale ls condition see meyer 1987 the ls condition includes the normal and many other asymmetric and leptokurtic distributions commonly used in finance in this paper we argue that this condition is also sufficient for expected utility to imply drawdown based performance measure rankings because for investment funds satisfying the ls condition it does not matter whether funds are ranked with the sharpe ratio or with a drawdown based performance measure as the rankings are identical hence the same conditions that provide an expected utility foundation for the sharpe ratio also provide an expected utility foundation for drawdown based performance measures theoretically drawdown based performance measures are as good as the sharpe ratio

ex post regret and the decentralized sharing of information abstract firms reveal private information about the value of investment through their investment decisions as a consequence they may have ex post regret once they see other firms investments we define a notion of rational expectations equilibrium for games which imposes a no regret property in this equilibrium all firms make the same investment decision but despite the absence of ex post regret the investment herd can be inefficient in addition equilibrium might not exist we introduce a notion of probabilistic existence and identify conditions under which if the number of firms is large enough information comes out so that investment herds are first best efficient with high probability and equilibrium exists with high probability journal of economic literatureclassification numbers c7 d8

assessing and valuing the non linear structure of hedge fund returns several studies have put forward the non linear structure and option like features of returns associated with hedge fund strategies the authors provide a statistical methodology to test for such non linear features with the returns on any benchmark portfolio they estimate the portfolio of options that best approximates the returns of a given hedge fund account for this search in the statistical testing of the contingent claim features and test whether the identi ed non linear features have a positive value the authors nd that not all categories of funds exhibit signi cant non linearities and that only a few strategies as a group provide signi cant value to investors individual funds may still provide value in

performance characteristics of hedge funds and commodity funds natural vs spurious biases it is well known that the pro forma performance of a sample of investment funds contains biases these biases are documented in brown goetzmann ibbotson and ross 1992 using mutual funds as subjects the organization structure of hedge funds as private and often offshore vehicles makes data collection a much more onerous task amplifying the impact of performance measurement biases theis paper reviews these biases in hedge funds we also propose using funds of hedge funds to measure aggregate hedge fund performance based on the idea that the investment experience of hedge fund investors can be used to estimate the performance of hedge funds

detecting structural breaks and identifying risk factors in hedge fund returns a bayesian approach abstract extending previous work on asset based style factor models this paper proposes a model that allows for the presence of structural breaks in hedge fund return series we consider a bayesian approach to detecting structural breaks occurring at unknown times and identifying relevant risk factors to explain the monthly return variation exact and efficient bayesian inference for the unknown number and positions of the breaks is performed by using filtering recursions similar to those of the forward backward algorithm existing methods of testing for structural breaks are also used for comparison we investigate the presence of structural breaks in several hedge fund indices our results are consistent with market events and episodes that caused substantial volatility in hedge fund returns during the last decade

option pricing and replication with transactions costs transactions costs invalidate the black scholes arbitrage argument for option pricing since continuous revision implies infinite trading discrete revision using black scholes deltas generates errors which are correlated with the market and do not approach zero with more frequent revision when transactions costs are included this paper develops a modified option replicating strategy which depends on the size of transactions costs and the frequency of revision hedging errors are uncorrelated with the market and approach zero with more frequent revision the technique permits calculation of the transactions costs of option replication and provides bounds on option prices

hedge fund performance 1990 2000 do the money machines really add value we investigate the claim that hedge funds offer investors a superior risk return tradeoff we do so using a continuous time version of dybvig s 1988a 1988b payoff distribution pricing model the evaluation model which does not require any assumptions with regard to the return distribution of the funds to be evaluated is applied to the monthly returns of 77 hedge funds and 13 hedge fund indices from may 1990 april 2000 the results show that as a stand alone investment hedge funds do not offer a superior risk return profile we find 12 indices and 72 individual funds to be inefficient with the average efficiency loss amounting to 2 76 per annum for indices and 6 42 for individual funds part of the inefficiency cost of individual funds can be diversified away funds of funds however are not the preferred vehicle for this as their performance appears to suffer badly from their double fee structure looking at hedge funds in a portfolio context results in a marked improvement in the evaluation outcomes seven of the 12 hedge fund indices and 58 of the 72 individual funds classified as inefficient on a stand alone basis are capable of producing an efficient payoff profile when mixed with the s p 500 the best results are obtained when 10 20 of the portfolio value is invested in hedge funds

coordinating research through research joint ventures abstract in a simple model we show that a joint venture can implement the rates of investment that maximize joint profit when firms research abilities are private information this can be done with budget balance even though there are participation constraints there is no conflict between budget balance and participation constraints because firms payoffs can depend on ex post signals of abilities the conflict between budget balance and participation constraints is restored when both abilities and rates of investment are unobservable we give a condition under which the profit maximizing rates of investment can be implemented if we relax budget balance

does the choice of performance measure influence the evaluation of hedge funds abstract the sharpe ratio is adequate for evaluating investment funds when the returns of those funds are normally distributed and the investor intends to place all his risky assets into just one investment fund hedge fund returns differ significantly from a normal distribution for this reason other performance measures for hedge fund returns have been proposed in both the academic and practice oriented literature in conducting an empirical study based on return data of 2763 hedge funds we compare the sharpe ratio with 12 other performance measures despite significant deviations of hedge fund returns from a normal distribution our comparison of the sharpe ratio to the other performance measures results in virtually identical rank ordering across hedge funds