okun s coefficient a comment this paper reassesses a finding by martin prachowny 1993 that the value of the okun coefficient for the united states linking unemployment changes to output changes is only around 0 67 rather than around the more typical value of 2 25 using a cointegration framework and the same data sets as prachowny we find for one of the data sets that the okun coefficient is much closer to a value of 2 25 which supports previous research work

optimal consumption and investment with transaction costs and multiple risky assets we consider the optimal intertemporal consumption and investment policy of a constant absolute risk aversion cara investor who faces fixed and proportional transaction costs when trading multiple risky assets we show that when asset returns are uncorrelated the optimal investment policy is to keep the dollar amount invested in each risky asset between two constant levels and upon reaching either of these thresholds to trade to the corresponding optimal targets an extensive analysis suggests that transaction cost is an important factor in affecting trading volume and that it can significantly diminish the importance of stock return predictability as reported in the literature this paper studies the optimal intertemporal consumption and investment policy of an investor with a constant absolute risk aversion cara preference and an infinite horizon the investor can trade in one risk free asset and n 1 risky assets in contrast to the standard setting the investor faces both fixed and proportional transaction costs in trading any of these risky assets in the absence of transaction costs and when risky asset prices follow geometric brownian motions the optimal investment policy is to keep a constant dollar amount in each risky asset as shown by merton 1971 this trading strategy requires continuous trading in all the risky assets in addition the optimal consumption is affine in the total wealth in the presence of transaction costs however trading continuously in a risky asset would incur infinite transaction costs therefore risky assets are traded only infrequently in this case the literature on optimal consumption and investment with multiple risky assets subject to transaction costs is limited leland 2000 examines a multiasset investment fund that is subject to transaction costs and capital gains taxes under the assumption that the fund has an exogenous target for each risky asset he develops a relatively simple numerical procedure to compute the no transaction region akian menaldi and sulem 1996 consider an optimal consumption and investment problem with proportional transaction costs for

smooth trading with overconfidence and market power we describe a symmetric continuous time model of trading among relatively overconfident oligopolistic informed traders with exponential utility traders agree to disagree about the precisions of their continuous flows of gaussian private information with enough disagreement an equilibrium exists in which prices reveal the average of all traders signals immediately but traders continue to trade gradually towards target inventories the price is a linear function of a trader s inventory the derivative of a trader s inventory and the average other traders valuations prices reflect a keynesian beauty contest faster than equilibrium trading generates flash crashes jel d8 d43 d47 g02 g14

panel tests of okun s law for ten industrial countries donald g freeman i introduction okun s law describes an empirical regularity between unemployment and real output growth each extra percentage point in the unemployment rate above four percent i e full employment has been associated with about a three percent decrement in real gnp okun 1962 9 1 okun s law has proved to be one of the more durable relationships in modern macroeconomics and is now often presented as an element of core beliefs as in textbooks by hall and taylor 1993 77 and in policy discussions by blinder 1997 durability and simplicity being relatively scarce commodities in macroeconomics okun s law is appealing as a shorthand guide to policy outcomes whether okun s law travels well is another question cross country comparisons of the relationship between unemployment and output have been estimated for other countries by knoester 1986 paldam 1987 and moosa 1997 among others but magnitudes vary depending on country and time period estimates in these papers of the increase in output growth associated with unemployment reduction of one percent range from a low of around two percent in the u s and canada to three to five percent in europe to more than 10 percent in japan with estimates for europe tending to be higher for more recent time periods because of the way that okun s law is framed tests of its proposition involve two imposing empirical problems first as usually stated the law refers to the relationship between departures of real gdp 2 and unemployment from their long run or equilibrium trends often referred to as potential gdp and the natural rate of unemployment respectively these equilibrium trends must be estimated either by time series methods as in moosa 1997 or by construction using a modified production function approach in which potential output is estimated using fully employed inputs as in gordon 1984 or adams and coe 1989 either of these fapproaches invites considerable criticism of assumptions and methods see for example the comments of clark 1984 and of baily 1984 on gordon 1984 second in formulating his law okun seems clearly not to be referring to a ceteris paribus relationship between changes in the unemployment rate and changes in real gdp writing later okun posited that other factors and inputs would be changing pari passu with employment the 3 percent result from a reduction of one percent in the unemployment rate implies that considerable output gains in a period of rising utilization rates stem from some or all of the following induced increases in the size of the labor force longer average weekly hours and greater productivity okun 1970 p 140 thus a complete specification of the effect of changing unemployment rates on output would include factors such as capital inputs labor hours and participation rates all measured as deviations from long run trends this article addresses these two obstacles by using a recent trend cycle decomposition developed by baxter and king 1999 to measure gaps in output unemployment capital stock and the labor force the baxter king bandpass filter extracts the trend component of economic time series by eliminating both high frequency those less than two years and low frequency more than eight years components it is both flexible and easy to implement by using the bandpass filter to filter all the time series using the same methodology this paper departs from previous research of prachowny 1993 and attfield and silverstone 1997 incorporating capital and labor to augment estimates of okun s law additionally using the bandpass filter allows the estimates in this article to incorporate more timely data reflecting the shift to lower levels of unemployment in the u s and higher levels of unemployment in europe and japan during the 1990s the latest year of observation for the constructed data sets of gordon and of adams and coe used for example by prachowny 1993 and attfield and silverstone 1997 is 1988

environmental regulation and competitiveness empirical evidence on the porter hypothesis from european manufacturing sectors abstract this paper investigates the weak and strong versions of porter hypothesis ph focusing on the manufacturing sectors of 17 european countries between 1997 and 2009 the hypothesis that well crafted and well enforced regulation would benefit both the environment and the firm was originally proposed by porter 1991 and porter and van der linde 1995 to date the literature has analyzed the impact of environmental regulation on innovation and on productivity mostly in separate analyses and focusing on the usa the few existing contributions on europe study the effect of environmental regulation either on green innovation or on performance indicators such as exports we instead look at overall innovation and productivity impacts first focusing on overall innovative activity allows us to account for potential opportunity costs of induced innovations second productivity impacts are arguably the most relevant indicators for the strong ph as a proxy of environmental policy stringency we use pollution abatement and control expenditures pace one of the few sectoral level indicators available we remedy upon its main drawback namely potential endogeneity by adopting an instrumental variable estimation approach we find evidence of a positive impact of environmental regulation on the output of innovation activity as proxied by patents thus providing support in favor of the weak ph this result is in line with most of the literature on the other front we find no evidence in favor of the strong ph as productivity appears to be unaffected by the degree of pollution control and abatement efforts

okun s law theoretical foundations and revised estimates okun s law has been accepted as an empirical regularity that predicts a 3 percentage point increase in output for every 1 point reduction in the unemployment rate but only because other facts such as weekly hours induced labor supply and productivity tend to rise as well when output gaps are estimated for the u s economy with a production function approach using two different data sets for potential output and nairu it is found that the marginal contribution of a 1 point reduction in unemployment is only about two thirds percent increase in output changes in weekly hours and capacity utilization have independent effects on the output gap copyright 1993 by mit press

dynamic portfolio choice with frictions abstract we show how portfolio choice can be modeled in continuous time with transitory and persistent transaction costs multiple assets multiple signals predicting returns and general signal dynamics the objective function is derived from the limit of discrete time models with endogenous transaction costs due to optimal dealer behavior we solve the model explicitly and the intuitive solution is also the limit of the solutions of the corresponding discrete time models we show how the optimal high frequency trading strategy depends on the nature of the trading costs which in turn depend on dealers inventory dynamics finally we provide equilibrium implications and illustrate the model s broader applicability to micro and macro economics monetary policy and political economy

environmental regulations and productivity growth the case of fossil fueled electric power generation this paper measures and analyzes the effect of sulfur dioxide emission restrictions on the rate of productivity growth in the electric power industry over the 1973 79 business cycle a firm specific measure of regulatory intensity is developed which depends on the severity of the emission standard the extent of enforcement and the unconstrained emission rate relevant to each utility the results indicate that emission regulations result in significantly higher generating costs primarily from the increased use of low sulfur fuels the average rate of productivity growth was reduced by 0 59 percentage points per year for constrained utilities

environmental innovation and environmental performance abstract by estimating a simultaneous panel data model of environmental innovation and toxic air pollution this paper identifies bi directional causal links between the two we study a panel of 127 manufacturing industries over the period 1989 2004 pollutant emissions are an implicit measure of policy stringency and environmental patent counts are used to measure environmental innovation after accounting for the joint endogeneity we find that environmental innovation is an important driver of reductions in us toxic emissions conversely we find that tightened pollution targets induce environmental innovation however our estimates indicate that the environmental policy multiplier the proportionate contribution of induced innovation to long run emission reduction is small

r d appropriability opportunity and market structure new evidence on some schumpeterian hypotheses one of the largest bodies of literature in the field of industrial organization is devoted to the interpretation and testing of several hypotheses advanced by joseph schumpeter 1950 concerning innovation and industrial market structure one set of hypotheses focuses on the role of firm size as a determinant of r d spending and the rate of technological advance another set focuses on the effect of market concentration on r d and technological advance in this paper we reexamine the latter set of hypotheses at the industry level using new data on r d appropriability and technological opportunity collected by levin et al 1984 in a survey of r d executives in 130 industries

asset prices and liquidity in an exchange economy i develop an asset pricing model in which financial assets are valued for their liquidity the extent to which they are useful in facilitating exchange as well as for being claims to streams of consumption goods the implications for average asset returns the equity premium puzzle and the risk free rate puzzle are explored in a version of the model that nests the work of mehra and prescott 1985

output and unemployment dynamics in the united states 1950 1985 for us data over 1950 1985 the stochastic components of gnp growth and the unemployment rate appear to be stationary and there is substantial feedback between these variables the unconditional mean rate of unemployment in a joint model thus provides a natural benchmark in discussions of the business cycle a bivariate var model is used to describe output unemployment dynamics to estimate the degree of persistence of output innovations and to decompose output into trend and cycle the bivariate results are interpreted using a restricted var and it is shown that a closely related cyclical measure can be obtained directly from the okun s law equation

productivity growth and environmental regulation in mexican and u s food manufacturing many argued during the nafta debate that trade liberalization would favor mexican over u s food processors especially because of lax environmental laws south of the border we find through an examination of profit functions that productivity growth in mexico has outstripped that in the united states suggesting free trade indeed will benefit mexican suppliers u s pollution regulations have had no impact on the profitability or productivity of u s food manufacturing in contrast mexico s swiftly rising environmental standards have enhanced food processors productivity growth corroborating the porter hypothesis pollution law therefore has favored mexican over u s food processing but for reasons few had anticipated

an analysis on the structural stability of okun s law a cross country study okun s law postulates an inverse relationship between movements of the unemployment rate and the real gross domestic product gdp this article investigates okun s law for 15 oecd countries and checks for its the structural stability by using data on employment and the labour force whether structural instability is caused either from the demand side or supply side is inferred

unit root tests persistence and the unemployment rate of the u s states author affiliation diego romero avila department of economics carretera de utrera km 1 pablo de olavide university 41013 seville spain dromtor upo escarlos usabiaga professor department of economics carretera de utrera km 1 pablo de olavide university 41013 seville spain cusaiba upo es corresponding author acknowledgment the authors would like to thank seminar participants at the pablo de olavide university and dg economics at the european central bank carlos usabiaga acknowledges the financial support from centro de estudios andaluces ecod1 05 033 special thanks go to junsoo lee and nikolay gospodinov for making available to us the codes to implement some of the techniques used in the paper and to two anonymous referees for suggestions that substantially improved the paper the usual disclaimer applies 1 introductionthe high persistence in unemployment rates observed in the developed world since the first oil shock has led to a vivid debate over which paradigm can better explain the behavior of unemployment rates the traditional strand of the literature that forms the basis of the natural rate theory phelps 1967 1968 friedman 1968 assumes that the unemployment rate evolves around an equilibrium level describing stationary fluctuations this equilibrium level or natural rate is set depending on fundamentals of the economy while initially the absence of theories explaining the determination of the natural rate meant that in practice it was taken to be constant and exogenous subsequent developments have attempted to identify the structural factors behind differences across economies and over time including labor productivity technological change real interest rates real exchange rates and energy prices to name a few see phelps 1994 phelps and zoega 1998 according to the structuralist view phelps 1994 most shocks to unemployment are temporary but occasionally the natural rate permanently changes and is affected by variations in the aforementioned structural factors as a consequence the unemployment rate may be characterized as a process that is stationary once a small number of structural breaks are allowed for in contrast to the natural rate and structuralist approaches the hysteresis hypothesis see blanchard and summers 1986 1987 implies that the unemployment rate is path dependent and temporary shocks can affect unemployment permanently 1 while hysteresis is thought to imply that the natural rate is conditioned by the level of unemployment recorded in the past persistence in unemployment which is a special case of the natural rate hypothesis entails a slow adjustment process of reversion toward the mean thus hysteresis implies that unemployment is characterized by a unit root while persistence is characterized by a near unit root in the latter case shocks to unemployment though long lasting would not have a permanent effect to discriminate among theories explaining the behavior of unemployment rates unit root tests have been widely applied the hysteresis hypothesis has been formulated as a unit root process and its rejection lends support to the natural rate hypothesis if no breaks are included in the specification and the structuralist hypothesis if breaks are allowed for the purpose of this article is to investigate which theoretical paradigm most closely represents the behavior of unemployment rates in the states of the united states over the period 1976 2004 we first apply the individual lagrange multiplier lm t statistic proposed by schmidt and phillips 1992 to monthly data and we fail to reject the null hypothesis of a unit root in unemployment for forty states perron 1989 pointed out that the presence of structural changes could favor the nonrejection of the unit root null if they are not properly accounted for therefore we employ the minimum lm t statistic allowing for up to two endogenous changes in level proposed by lee and strazicich 2003

portfolio choice and pricing in illiquid markets abstract this paper studies portfolio choice and pricing in markets in which immediate trading may be impossible it departs from the literature by removing restrictions on asset holdings and finds that optimal positions depend significantly and naturally on liquidity when expected future liquidity is high agents take more extreme positions given that they do not have to hold those positions for long when they become undesirable consequently larger trades should be observed in markets with more frequent trading liquidity need not affect the price significantly however because liquidity has offsetting impacts on different agents demands this result highlights the importance of unrestricted portfolio choice the paper draws parallels with the transaction cost literature and clarifies the relationship between the price level and the realized trading frequency in this literature

episodic liquidity crises cooperative and predatory trading we describe how episodic illiquidity arises from a breakdown in cooperation between market participants we first solve a one period trading game in continuous time using an asset pricing equation that accounts for the price impact of trading then in a multi period framework we describe an equilibrium in which traders cooperate most of the time through repeated interaction providing apparent liquidity to one another cooperation breaks down when the stakes are high leading to predatory trading and episodic illiquidity equilibrium strategies that involve cooperation across markets lead to less frequent episodic illiquidity but cause contagion when cooperation breaks down why is illiquidity rare and episodic pastor stambaugh 2003 detect only 14 aggregate low liquidity months over the time period 1962 to 1999 despite being of significant magnitude most of the episodes were short lived and were followed by long periods of liquidity 1 the origin of this empirical observation still remains a puzzle in this paper we attempt to shed light on this puzzle by developing a theoretical model in which a breakdown in cooperation between traders in the market manifests itself in predatory trading this mechanism leads to sudden and short lived illiquidity we develop a dynamic model of trading based on liquidity needs during each period a liquidity event may occur in which a trader is required to liquidate a large block of an asset in a relatively short time period this need for liquidity is observed by a tight oligopoly whose members may choose to predate or cooperate predation involves racing and fading the distressed trader to the market

asymmetry in okun s law in this paper we support the proposition that the output unemployment relationship as represented by okun s law is asymmetric okun s coefficients are defined based on a dynamic model that allows for asymmetry in the relationship between cyclical output and unemployment using data from the united states for the post war period our results show that the short run effects of positive cyclical output on cyclical unemployment are quantitatively different from those of negative ones and the data are consistent with the proposition that cyclical unemployment is more sensitive to negative than to positive cyclical output several theoretical

cyclical output cyclical unemployment and okun s coefficient a new approach estimates of okun s coefficient are obtained using new estimates of cyclical gnp and cyclical unemployment rates for the post war usa empirical estimates of the coefficient are near 0 25 somewhat smaller in magnitude than other recent estimates obtained applying similar econometric techniques to different estimates of cyclical output and unemployment tests fail to reject the hypothesis of parameter stability across an hypothesized break between the third and fourth quarters of 1973 suggesting similar relationships between cyclical output and unemployment both before and after the supply shocks of the 1970s

environmental regulation and the export dynamics of energy technologies abstract the pollution haven hypothesis affirms that an open market regime will encourage the flow of low technology polluting industries toward developing countries because of potential comparative advantages related to low environmental standards in contrast the hypothesis suggested by porter and van der linde claims that innovating firms operate in a dynamic competitive situation which allows global diffusion of environmental friendly technologies environmental regulation may represent a relevant mechanism through which technological change is induced in this way countries that are subject to more stringent environmental regulations may become net exporters of environmental technologies this paper provides new evidence on the evolution of export flows of environmental technologies across different countries for the energy sector advanced economies particularly the european union have increasingly focused on the role of energy policies as tools for sustaining the development path the kyoto protocol commitments together with growing import dependence on energy products have brought attention to the analysis of innovation processes in this specific sector the analysis uses a gravity model in order to test the determinants and the transmission channels through which environmental technologies for renewable energies and energy efficiency are exported to advanced and developing countries our results are consistent with the porter and van der linde hypothesis where environmental regulation represents a significant source of comparative advantages what strongly emerges is that the stringency of environmental regulation supplemented by the strength of the national innovation system is a crucial driver of export performance in the field of energy technologies

transaction costs and asset prices a dynamic equilibrium model in this article we study the effects of transaction costs on asset prices we assume an overlapping generations economy with a riskless liquid bond and many risky stocks carrying proportional transaction costs we obtain stock prices and turnover in closed form surprisingly a stock s price may increase in transaction costs and a more frequently traded stock may be less adversely affected by an increase in transaction costs calculations based on the marginal investor overestimate the effects of transaction costs for realistic parameter values transaction costs have very small effects on stock prices but large effects on turnover

linking induced technological change and environmental regulation evidence from patenting in the u s auto industry a b s t r a c t this article uses a carefully screened patent database in automobile emission control technologies and a detailed regulatory action analysis to examine firms innovation in response to u s technology forcing auto emissions standards enacted between 1970 and 1998 the study finds that under the performance based technology forcing pbtf auto emissions regulations both automakers and compo nent suppliers innovated and introduced more advanced emission control technologies for automobile applications the study also shows that stringent pbtf regulation temporarily induced domestic u s firms to become more innovative than foreign firms that operated in the local u s market during the early phase of the regulatory regime findings of this research strongly imply that government intervention in the form of technology forcing regulation can drive firms to invest in technological innovation

pricing options in an extended black scholes economy with illiquidity theory and empirical evidence this article studies the pricing of options in an extended black scholes economy in which the underlying asset is not perfectly liquid the resulting liquidity risk is modeled as a stochastic supply curve with the transaction price being a function of the trade size consistent with the market microstructure literature the supply curve is upward sloping with purchases executed at higher prices and sales at lower prices optimal discrete time hedging strategies are then derived empirical evidence reveals a significant liquidity cost intrinsic to every option copyright 2006 oxford university press

determinants of environmental innovation in us manufacturing industries abstract this paper provides new evidence on the determinants of environmental innovation we employ panel data models to study how environmental innovation by us manufacturing industries responded to changes in pollution abatement expenditures and regulatory enforcement during the period 1983 through 1992 we find that 1 environmental innovation as measured by the number of successful environmental patent applications granted to the industry responded to increases in pollution abatement expenditures however 2 increased monitoring and enforcement activities related to existing regulations did not provide any additional incentive to innovate we also find some empirical evidence that environmental innovation is more likely to occur in industries that are internationally competitive

revisiting the okun relationship our article revisits the okun relationship between observed unemployment rates and output gaps we include in the relationship the effect of labour market institutions as well as age and gender effects our empirical analysis is based on 20 oecd countries over the period 1985 2013 we find that the share of temporary workers which includes a high and rising share of young workers played a crucial role in explaining changes in the okun coefficient the impact of the output gap on the unemployment rate over time the okun coefficient is not only different for young prime age and older workers but also it decreases with age from a policy perspective it follows that an increase in economic growth will not only have the desired outcome of reducing the overall unemployment rate but it will also have the distributional effect of lowering youth unemployment

testing okun s law theoretical and empirical considerations using fractional integration abstractfull employment remains at the center of any economic policy following okun s conclusion regarding the trade off relation between unemployment and real gross national product growth new s