on the exclusion of assets from tests of the mean variance efficiency of the market portfolio this paper presents an analysis of the testability of the mean variance efficiency of a market index when the returns on some components of the index itself are not perfectly observable the results are basically not supportive of the notion that mean variance efficiency is testable on a subset of the assets bounding the market share of the missing asset and its expected return is not sufficient to produce a valid test when the variance of the missing asset is bounded and the amount of wealth that might be missing is small it is possible in principle to reject correctly the mean variance efficiency of a market index in his famous critique of the asset pricing theory tests roll 7 concludes that the only testable hypothesis associated with the generalized two parameter asset pricing model of black 1 is that the market portfolio is mean variance efficient it has been emphasized by ross 10 and roll 7 that the mean variance efficiency of the market portfolio is mathematically equivalent to a positive linear relation between expected returns and the betas calculated against such a portfolio roll 7 deduces that the theory capm is not testable unless the exact composition of the market portfolio is known and used in the tests this implies that the theory is not testable unless all individual assets are included in the sample errors of type one or two might occur when a market proxy is used instead of the true market portfolio even if the ex ante true expected returns and the covariance variance matrix of the returns on all the assets are used these errors are the result of the choice of the portfolio and as roll puts it even a small misspecification of the proxy s composition can lead to the wrong conclusion the market proxy might be mean variance efficient while the true market portfolio is not and vice versa in principle however there are cases in which the above two conditions are not both necessary to reject the theory one such exception presented by roll 7 is the case in which no totally positive portfolio is efficient if any totally positive market proxy is used a large sample would reject the null hypothesis unambiguously while the market portfolio identification problem constitutes a severe limitation to the testability of the theory the question of the mean variance efficiency of a particular market index with respect to a subset of assets is a typical problem of statistical inference the mean variance efficiency can be tested directly or by

mimicking portfolios and exact arbitrage pricing we characterize the sets of mimicking positions with returns that can serve in place of factors in an exact k factor arbitrage pricing relation for a set of n assets all of the sets are k dimensional nonsingular linear transformations of each other we interpret three examples of such transformations and discuss empirical considerations we provide conditions under which the mimicking positions can be expressed as portfolios and we characterize the relation between mimicking portfolios and the minimumvariance frontier

forward exchange bias hedging and the gains from international diversification of investment portfolios abstract the gains to the us investor from international diversification of investment portfolios are examined for portfolio strategies that hedge and strategies that do not hedge exchange rate risk via the interbank forward market using the sharpe performance index and stochastic dominance as performance measures almost all the unhedged strategies outperformed the hedged strategies for 1985 1988 the opposite held for 1981 1984 the results are explained by the biasedness of forward rates in predicting future spot rates jel f30

equipment investment and growth in developing countries abstract differences in equipment investment or equipment prices account for large variations in growth rates across countries an important task is to understand the economic mechanism underlying the equipment growth nexus and its policy implications in order to study this issue this paper develops a model in which growth is driven by the adoption of technologies that are embodied in equipment i show that this model can quantitatively account for the observed cross country relationships between equipment investment equipment prices and growth i find that the competitive equilibrium is characterized by inefficiently low levels of learning and too slow growth and study which policies are able to remedy this inefficiency

imperfect competition expectations and the multiple effects of monetary growth in a monetary overlapping generations model with an imperfectly competitive labor market in which output is below its full employment level it is shown that different backward looking rules for forecasting inflation lead to different steady states despite yielding no forecast errors in the steady state and in many cases none in the short or medium run either higher monetary growth raises output in some steady states in others has no effect and in others lowers it this contrasts with ad hoc or competitive macromodels where the absence of forecast errors in the steady state usually defines it and its properties uniquely copyright 1992 by royal economic society

using generalized method of moments to test mean variance efficiency this paper develops tests of unconditional mean variance efflciency under weak distributional assumptions using a generalized method of moments framework these tests are potentially more robust than commonly employed tests which rely on the assumption that asset returns are normally distributed and temporarily i i d using returns for size based portfolios from 1926 to 1988 we show that the conclusion concerning the mean variance effilciency of market indexes can be sensitive to the test considered the application of multivariate statistical techniques in financial economics has become common practice in recent years much of the development has been in the area of testing asset pricing models the assumption that asset returns follow a time invariant multivariate normal distribution permits tests of restrictions on model parameters in a pooled time series cross section framework these tests can be interpreted as tests of the mean variance efficiency of a portfolio or combination of portfolios gibbons 1982 jobson and korkie 1982 stambaugh 1982 shanken 1985 1987 kandel and stambaugh 1987 mackinlay 1987 and gibbons ross and shanken 1989 are examples of work presenting multivariate tests of the capital asset pricing model connor and korajczyk 1988 and lehmann and modest 1988 present multivariate tests of the arbitrage pricing model breeden gibbons and litzenberger 1989 present multivariate tests of the consumption based capm although these papers assume the normality of asset returns little analysis has been conducted to understand the sensitivity of the inferences to violations of this assumption 2 3

decomposing learning by doing in new plants the paper examines learning by doing in the context of a production function in which the other arguments are labor human capital physical capital and vintage as a proxy for embodied technical c

technology adoption learning by doing and economic growth abstract we develop a model in which firms choose which technologies to adopt as well as the timing of such adoptions in between adoptions a firm accumulates expertise in its technology which allows it to operate the technology more efficiently thus there is firm specific learning by doing for certain parameterizations of the model and appropriate initial distributions of technologies and expertise equilibria are characterized by positive and constant growth of per capita output and positive but nonconstant growth of each firm s output we find firms adoption decisions and output growth depend upon the efficiency of capital markets journal of economic literature classification numbers o41 o33

sticky prices as coordination failure this paper links the coordination failure and menu cost approaches to the microeconomic foundations of keynesian macroeconomics if a firm s desired price is increasing in others prices then the gain from price adjustment after a nominal shock is greater if others adjust this strategic complementarity leads to multiple equilibria in the degree of rigidity welfare may be much higher in the equilibria with less rigidity thus nominal rigidity arises from a failure to coordinate price changes jel e12 e30 keynesian macroeconomics waned in the 1970 s because economists grew disenchanted with its weak microeconomic foundations the central difficulty was that keynesian models were based on ad hoc rigidities in nominal wages and prices the 1980 s produced two approaches to reviving keynesian theory the menu cost literature n gregory mankiw 1985 george akerlof and janet yellen 1985 seeks to provide rigorous explanations for nominal rigidities these papers argue that small frictions in price setting are enough to produce large nominal rigidities in contrast the coordination failure literature russell cooper and andrew john 1988 abandons nominal rigidities and seeks alternative foundations for keynesian models the central idea is that many economic activities such as production e g john bryant 1983 trade e g peter diamond 1982 and investment e g nobuhiro kiyotaki 1988 exhibit synergism or strategic complementarity one agent s optimal level of activity depends positively on others activity strategic complementarity can lead to multiple equilibria with high activity equilibria superior to low activity equilibria thus an economy may be stuck in an underemployment equilibrium even though a superior equilibrium exists models with nominal rigidities and models with coordination failures are often presented as competing paradigms 1 this paper shows that this view is incorrect we take a step toward unifying the foundations of keynesian economics by showing that the two sets of ideas are highly complementary nominal rigidity arises from a failure to coordinate price changes this failure has the essential features of coordination failures in previous models flexibility in one firm s price increases the incentives for other firms to make their prices flexible this strategic complementarity leads to multiple equilibria in the degree of nominal rigidity equilibria with less rigidity more active price adjustment are often pareto superior to equilibria with more rigidity these results contribute to our understanding both of coordination failure and of nominal rigidity the range of keynesian phenomena explained by coordination failures is greatly expanded previous coordination failure models contain only real variables and thus ascribe no role to monetary policy or other determinants of nominal spending our results suggest that coordination failure is at the root of inefficient nonneutralities of money theories of nominal rigidities gain new empirical and policy im

on the jensen measure and marginal improvements in portfolio performance a note the marginal performance contribution made by new assets in a portfolio is identified the maximum change in a portfolio s sharpe performance from the addition of new assets is a simple function of a generalized jensen index and the unexplained covariances from a multivariate market model deviations from a higher dimension market line may be used to rank the desirability of asset additions to an existing portfolio statistical tests for the equality of the performance contributions by new assets is possible the portfolio performance measures of treynor 11 and jensen 12 are based on the systematic or beta measure of risk when originally developed it was advocated that these measures of performance were useful for comparing and ranking performances of various portfolios after many years of use in this area it was demonstrated by roll 7 and ross 8 that it is theoretically inappropriate to use these performance measures for this purpose since differences in portfolios performance indicate only inefficiency in the index used for the computation of beta dybvig and ross 1 subsequently proved that a portfolio can be improved by adding or shorting a small investment in another asset if the asset lies above or below the security market line a potentially important use of the market line was therefore preserved the purpose of this note is the development of a procedure which identifies the exact performance contribution made by one or more assets when they enter the investor s optimal portfolio of assets it is demonstrated that the change in squared sharpe 10 performance is a simple function of a generalized jensen index and the unexplained covariances from a multivariate market model new assets may be ranked according to the magnitude of their performance contribution the improvements in a portfolio are easily computable from the same linear regression employed to calculate an asset s jensen measure thus the appeal of the security market line as a useful financial tool may be preserved the first section briefly establishes the efficient set algebra required to develop the marginal contribution made by new assets in a portfolio section ii presents the performance contribution dependent on the number of new assets and whether partial or full optimal adjustment of the portfolio weights are permitted section iii concludes the note

stabilisation policy targets and unemployment in imperfectly competitive economies this paper argues that the rate of equilibrium unemployment depends on the objectives of the central bank in a model where the central bank uses monetary policy to stabilise the economy we show that unemployment and inflation will be lower with an inflation target than with targets for output money or nominal gdp the intuition for this is that the elasticities of demand in both the product and the labour markets are greater when there is an inflation target we show that this leads to a lower mark up of price over marginal cost and makes wages more sensitive to unemployment

did the debt crisis cause the investment crisis there is now a large literature that attributes the investment decline in heavily indebted countries to the effects of the international debt crisis which began in 1982 however these countries also faced falling export prices and high world real interest rates in the early 1980s and these shocks could have directly caused investment to decline one way to test for debt effects is to see whether equations without any debt related information can nevertheless forecast the investment declines that these countries experienced this paper shows that such equations can forecast investment in many indebted countries and thus casts doubt on many debt related explanations for the investment declines

cross holdings estimation issues biases and distortions cross holding occurs when listed corporations own securities issued by other corporations we analyze the effect of cross holdings on market capitalization and return measures as well as implications for econometric testing of asset pricing theories we show that cross holdings generally distort standard market return and risk measures the magnitudes of such distortions are calculated for simulated economies by using a variety of crossholding patterns in addition cross holdings are shown to induce nonstationarity in the covariance matrix of security returns we examine the effect of this nonstationarity for estimating efficient frontiers and factor structures we also discuss the implications for risk return estimates in equilibrium asset pricing models article published by oxford university press on behalf of the society for financial studies in its journal the review of financial studies

potential performance and tests of portfolio efficiency abstract the potential performance of an asset set may be obtained by choosing the portfolio proportions to maximize the sharpe 1966 performance measure if a portfolio has a sharpe measure equivalent to the potential performance of the underlying set of assets then it is efficient multivariate statistical procedures for comparing potential performance and testing portfolio efficiency are developed and then evaluated using simulations two likelihood ratio statistics are then used to compare stock and bond indices against sets of 20 and 40 portfolios the procedures are also compared to the gibbons 1982 methodology for testing financial models

interactions of commitment and discretion in monetary and fiscal policies we consider monetary scal interactions when the monetary authority is more conservative than the scal with both policies discretionary 1 nash equilibrium yields lower output and higher price than the ideal points of both authorities 2 of the two leadership possibilities scal leadership is generally better with scal discretion monetary commitment yields the same outcome as discretionary monetary leadership for all realizations of shocks but scal commitment is not similarly negated by monetary discretion second best outcomes require either joint commitment or identical targets for both authorities output socially optimal and price level appropriately conservative or complete separation of tasks jel e61 e63

capital accumulation under technological progress and learning a vintage capital approach abstract in standard capital accumulation models all capital goods are equally productive and produce goods of the same quality however due to technological progress in reality it holds most of the time that newer capital goods are either more productive process innovation or produce goods of better quality product innovation implications of process innovation for the firm s investment policies are investigated while the output price development is subject to a business cycle and a given generation of capital goods gets more productive over time due to learning the problem is turned into an optimal control model that distinguishes the vintages of capital goods and where unlike most of the recent contributions it is possible to keep on investing in older technologies it is shown that i learning is one of the reasons why a firm may invest in old technologies even when apparently superior technologies are available ii investments in machines of a given age increase more over time under faster technological progress iii under faster technological progress investments are more vulnerable to output price developments and iv on average machines are older during recessions in deciding whether to invest in newer or older capital goods also the lower productivity due to aging versus differences in cost of discounting and acquisition have to be taken into account

multiplicity of cournot equilibria and involuntary unemployment abstract in an overlapping generations model with cournot competition on the goods market it is shown that a continuum of stationary states and perfect foresight trajectories exists with unemployment at arbitrary low wages decisive for this is the influence that different forecast functions have on the objective demand curve even though they are consistent with perfect foresight with an example it is shown that simple adaptive and constant memory forecast rules generate such unemployment equilibria the corresponding temporary equilibrium dynamics may display stable unemployment and unstable full employment equilibria journal of economic literatureclassification numbers d43 d51 e24

monopolistic competition and the effects of aggregate demand how important is monopolistic competition to an understanding of the effects of aggregate demand on output we ask the question at three levels can monopolistic competition by itself explain why aggregate demand movements affect output can it together with other imperfections generate effects of aggregate demand in a way that perfect competition cannot if so can it give an accurate account of the response of the economy to aggregate demand movements the answers are no yes and yes

imperfectly competitive cycles with keynesian and walrasian features abstract we consider a multi sector overlapping generations model with oligopolistic firms in the output markets and wage setting trade unions in the labour markets a coordination problem between firms creates multiple temporary equilibria which are either walrasian or of the keynesian unemployment type there exist many deterministic and stochastic equilibrium cycles fluctuating between keynesian recession and walrasian boom periods with arbitrarily long phases in each regime the cycles are in accordance with certain empirical regularities money is neutral and superneutral but appropriate countercyclical fiscal policies stabilize the cycles in a textbook keynesian way

international investment restrictions and closed end country fund prices some closed end country funds trade at large premiums relative to their net asset values this paper examines whether international investment restrictions raise country fund price net asset value ratios by segmenting international capital markets we test whether a relation exists between announcements of changes in investment restrictions and changes in these ratios using weekly data from may 1981 to january 1989 the results provide evidence that some foreign markets are at least partially segmented from the u s capital market

endogenous imperfectly competitive business cycles abstract we investigate how imperfect competition affects the occurrence and the properties of endogenous rational expectations business cycles in an overlapping generations model with constant returns to scale in production the model has explicit product and labor markets all characterized by monopolistic competition an implicit assumption of barriers to entry justifies that the number of firms is fixed even when positive profits occur it turns out that both market power of firms on the product markets and market power of unions on the labor markets make the occurrence of cycles more likely in particular imperfect competition on the product markets and the positive profits associated with it may have the effect that there is a cycle even if the labor supply curve is increasing in the real wage rate for competitive cycles is required not only a decreasing labor supply curve but a wage elasticity below 1 2 at stationary equilibrium market power on the labor markets may have the effect that imperfectly competitive cycles are in accordance with certain empirical regularities some well known some reported in the paper concerning fluctuations in output and involuntary unemployment since involuntary unemployment does not occur under perfect competition such regularities are incompatible with competitive cycles

roads out of poverty assessing the links between aid public investment growth and poverty reduction the authors develop a macroeconomic framework that captures links between aid public investment growth and poverty public investment is disaggregated into education infrastructure and health and affects both aggregate supply and demand dutch disease effects are captured by accounting for changes in the relative price of domestic goods the authors assess the impact of policy shocks on poverty by linking the model to a household survey they calibrate the model for ethiopia and simulate the changes in the allocation of aid and public investment the authors also calculate the amount by which foreign aid should increase to reach the poverty targets of the millennium development goals

a model of imperfect competition with keynesian features the recent literature on the reappraisal of keynes has viewed keynesian equilibria as arising when prices are fixed and effective demands and supplies are equilibrated through the adjustment of quantities one problem with this approach is that it lacks a theory of price determination in particular of why prices are fixed in the present paper we show that a number of keynesian features arise in a model in which prices are fully flexible but where agents have some monopoly power one advantage of this approach is that it provides a theory of the determination of both prices and quantities

decomposing technical change within the conventional neoclassical framework a distinction is sometimes made between productaugmenting and factor augmenting technical change a parallel distinction is commonly made between embodied and disembodied technical change with the former associated with factor and the latter with product augmentation disembodied change is commonly assumed to arise from increases in the stock of knowledge independently of the characteristics of the inputs used while embodied change relates to increases in the efficiency of inputs that is labor skills or the productivity of physical capital unfortunately this distinction is ambiguous changes in the efficiency of the inputs used are usually accompanied indeed made possible by increases in knowledge and conversely increases in the stock of knowledge often favor some inputs more than others including the capital goods of one vintage relative to those of another notwithstanding the ambiguity the concept of embodiment has intuitive appeal and this partly explains the focus on decomposing the sources of technical change that followed solow s 6 seminal paper but by the late 1960s a reader of the literature might have concluded that such decomposition was impossible for with merely time series data on inputs and output product augmenting and factor augmenting technical change are empirically indistinguishable in an important paper hall 3 showed that with data on used equipment prices and the interest rate embodied technical change and the deterioration function can in principle be calculated however the paucity of data on the price of used capital goods has allowed little progress in this direction the new longitudinal research database created by the u s bureau of the census now permits still another approach to the estimation of embodied technical change associated

long run implications of investment specific technological change an attempt is made to disentangle its effects from the more traditional hicksneutral form of technological progress the balanced growth path for the model is characterized and calibrated to u s national income and product account nipa data the quantitative analysis suggests that investment specific technological change accounts for the major part of growth jel e13 030 041 047

lyapunov stability in an evolutionary game theory model of the labour market in this paper the existence and stability of equilibria in an evolutionary game theory model of the labor market is studied by using the lyapunov method the model display multiple equilibria and it is shown that the nash equilibria of the static game are evolutionary stable equilibria in the game theory evolutionary set up in this vein a complete characterization of the dynamics of an evolutionary model of the labor market is provided

price rigidities and market structure conventional wisdom has it that a large part of the explanation of keynesian unemployment is the observed rigidities of wages and prices what has been lacking however is a satisfactory theory or conjunction of theories which explains how wages and prices can be at non market clearing levels the objective of this paper is to sketch out several alternative theoretical explanations of this phenomenon each in contrast with keynesian theory is consistent with the observation that as the economy goes into a recession real product wages do not increase and may in fact decrease all of the theories assume rational profit maximizing firms and all entail some important departure from the standard competitive paradigm the first three explanations represent minor adaptations of standard models

nonresponse in panel data the impact on estimates of a life cycle consumption function if missing observations in a panel data set are not missing at random many widely applied estimators may be inconsistent in this paper we examine empirically several ways to reveal the nature and severity of the selectivity problem due to nonresponse as well as a number of methods to estimate the resulting models using a life cycle consumption function and data from the expenditure index panel from the netherlands we discuss simple procedures that can be used to assess whether observations are missing at random and we consider more complicated estimation procedures that can be used to obtain consistent or efficient estimates in case of selectivity of attrition bias finally some attention is paid to the differences in identification consistency and efficiency between inferences from a single wave of the panel a balanced sub panel and an unbalanced panel

increasing returns and the foundations of unemployment theory current approaches to macroeconomic theory divide roughly into two basic schools of thought one approach typically associated with rational expectations views the economy as basically at or near walrasian market clearing equilibrium in which case it becomes very difficult to explain away convincingly the undeniable persistence at times of involuntary unemployment another approach views the underemployed economy as being in a state of temporary fixed price disequilibrium in which case aside from having to repress suspicions that the essence of effective demand failure might not have to do with prices fixed at wrong values there is a lot of rationalising to be done about why profitable adjustments are so slow this paper argues that something like an internally consistent theory of steady state involuntary unemployment is possible and even plausible the cornerstone of this third approach is increasing returns to scale which blocks unemployed agents from breaking out of a low level equilibrium trap unless there is overall coordination or stimulation a simple model is presented which contains the basic ideas

small menu costs and large business cycles a macroeconomic model of monopoly i introduction the conflict between modern neoclassical and traditional keynesian theories of the business cycle centers upon the pricing mechanism in neoclassical models prices are fully flexible they represent the continuous optimization of economic agents and the continuous intersection of supply and demand in keynesian models prices are often assumed to be sticky they do not necessarily equilibrate all markets at all times one of the reasons for the resurgence of the equilibrium approach to macroeconomics has been the absence of a theoretical underpinning for this keynesian price stickiness this note shows that sticky prices can be both privately efficient and socially inefficient the business cycle results from the suboptimal adjustment of prices in response to a demand shock to the extent that policy can stabilize aggregate demand it can mitigate the social loss due to this suboptimal adjustment in some keynesian models prices are simply exogenously fixed 2 in others agents must set their prices in advance of the transaction date the act of altering a posted price is certainly costly these costs include such items as printing new catalogs and informing salesmen of the new price yet these menu costs are small and therefore generally perceived as providing only a weak foundation for these fixed price models however this inference is flawed small menu costs can cause large welfare losses the claim that price adjustment costs are small does not rebut the claim that they are central to understanding economic fluctuations

block holding and keiretsu in japan the effects of capital markets liberalization measures on the stock market abstract long term block holding among large industrial corporations and financial institutions is prevalent in japan little is known about the implications of such business practice on portfolio returns we document the portfolio relationships of parent firms sub firms and specific industry portfolios and we hypothesize that these relationships have changed substantially in japan using certain measures for evaluating portfolios and mean variance spanning we test the hypothesis our empirical results suggest that market efficiency and integration of the japanese stock market may have been greatly enhanced by the japanese government s capital markets liberalization measures implemented in the 1970s and early 1980s

technology adoption with finite horizons the purpose of this paper is to study the relation between the age of an agent and her decisions about adopting new technologies to this end i analyze the optimal sequence of technology upgrades by an agent who lives for a finite period of time other characteristics of the environment are the existence of technology specific learning by doing technology growth and adoption costs a finite planning horizon implies that the technology adoption problem is non stationary and the frequency of adoptions changes over time this paper provides results for the computation of the optimal plan and explores numerically the life cycle pattern of technology switches adoptions may become more frequent as the agent grows older however the sign of the association between age and the adoption of new technologies is sensitive to variation in parameters this is not at odds with the findings of recent empirical studies

on the effectiveness of economic policy when competition is imperfect and expectations are rational abstract we study the consequences of imperfect competition in a macro model with only one imperfection that of labor market competition otherwise the model is clean agents are optimizers prices are endogenous and expectations are rational we show that although imperfect competition in itself can explain unemployment as is well known it does not in itself give strong support to the use of traditional fiscal policy in fighting unemployment fiscal policy will almost inevitably have real effects but only through a special effect that may be difficult to control in many cases fiscal policy cannot create full employment and it may very well have perverse effects

growth accounting when technical change is embodied in capital this paper revisits the hypothesis that technical change is embodied in capital it extends old results to make them more relevant to the contemporary debates about the adjustment of investment goods for quality change and about the role of embodied technical change as a source of economic growth it is shown that the failure to adjust capital for quality change has the effect of suppressing the quality effects into the conventional total factor productivity residual and it is found that approximately 20 percent of the residual growth of quality adjusted output could be attributed to embodied technical change copyright 1992 by american economic association