irreversible choice of uncertain technologies with network externalities in this article i explore the problem of sequential and irreversible technology choice in the presence of network externalities when the technologies stochastically evolve over time early potential users are shown to adopt an irreversible technology too early compared to the social optimum the effect of increasing the uncertainty of the technologies on an early potential user s decision is analyzed i find that the sponsor of new emerging technology might choose a research strategy that is too safe i also study the consequences of allowing side payments between generations of consumers and demonstrate that an ex post optimal standardization policy can impair ex ante social welfare

intertemporal labor supply and human capital accumulation we solve and estimate a dynamic model that allows agents to optimally choose their labor hours and consumption and that allows for both human capital accumulation and savings estimation results and simulation exercises indicate that the intertemporal elasticity of substitution is much higher than the conventional estimates and the downward bias comes from the omission of the human capital accumulation effect the human capital accumulation effect renders the life cycle path of the shadow wage relatively flat even though wages increase with age hence a rather flat life cycle labor supply path can be reconciled with a high intertemporal elasticity of substitution

taxes benefits and careers complete versus incomplete markets abstract an incomplete market life cycle model with indivisible labor makes career lengths and human capital accumulation respond to labor tax rates and government supplied non employment benefits we compare aggregate and individual outcomes in this individualistic incomplete market model with those in a comparable collectivist representative family model with employment lotteries and complete insurance markets the incomplete and complete market structures assign leisure to different types of individuals who are distinguished by their human capital and age these microeconomic differences distinguish the two models in terms of how macroeconomic aggregates respond to some types of government supplied non employment benefits but remarkably not to labor tax changes

technological expectations and adoption of improved technology abstract attention is focused upon the adoption demand rather than the creation supply of new technology which improves from time to time based on the expected flow of technological progress over which the firm demander has no control it must decide either to adopt the current best available technology or to postpone adoption the distinguishing features of the model are that more than one technological innovation is anticipated and expectations about the likelihood of such innovations are revised as time passes since the last innovation our analysis shows that the firm will adopt the current best practice if its technological lag exceeds a certain threshold moreover as time passes without new technological advances it may become profitable to purchase a technology that has been available even though it was not profitable to do so in the past

interest rates and currency prices in a two country world abstract this paper is a theoretical study of the determination of prices interest rates and currency exchange rates set in an infinitely lived two country world which is subject both to stochastic endowment shocks and to monetary instability formulas are obtained for pricing all equity claims nominally denominated bonds and currencies and these formulas are related to earlier closely related results in the theories of money finance international trade

uncertainty and the specificity of human capital this paper studies the choice between general and specific human capital a trade off arises because general human capital while less productive can easily be reallocated across firms accordingly the fraction of individuals with specific human capital depends on the amount of uncertainty in the economy our model implies that while economies with more specific human capital tend to be more productive they also tend to be more vulnerable to turbulence as such our theory sheds some light on the experience of japan where human capital is notoriously specific while japan benefited from this predominately specific labor force in tranquil times this specificity may also have been at the heart of its prolonged stagnation

nobel lecture the transformation of macroeconomic policy and research what i am going to describe for you is a revolution in macroeconomics a transformation in methodology that has reshaped how we conduct our science prior to the transformation macroeconomics was largely separate from the rest of economics indeed some considered the study of macroeconomics fundamentally different and thought there was no hope of integrating macroeconomics with the rest of economics that is with neoclassical economics others held the view that neoclassical foundations for the empirically determined macro relations would in time be developed neither view proved correct finn kydland and i have been lucky to be a part of this revolution and my address will focus heavily on our role in advancing this transformation now all stories about transformation have three essential parts the time prior to the key change the transformative era and the new period that has been affected by the change and that is the story i am going to tell how macroeconomic policy and research changed as a result of the transformation of macroeconomics from constructing a system of equations of the national accounts to an investigation of dynamic stochastic model economies

social security and retirement across the oecd abstract employment to population ratios differ markedly across organization for economic cooperation and development oecd countries especially for people aged over 55 years in addition social security features differ markedly across the oecd particularly with respect to features such as generosity entitlement ages and implicit taxes on social security benefits this study postulates that differences in social security features explain many differences in employment to population ratios at older ages this conjecture is assessed quantitatively with a life cycle general equilibrium model of retirement at ages 60 64 years the correlation between the simulations of this study s model and observed data is 0 67 generosity and implicit taxes are key features to explain the cross country variation whereas entitlement age is not

the excess sensitivity of layoffs and quits to demand excessive layoffs in bad times and excessive quits in good times both stem from the same weakness in practical employment arrangements the specific nature of worker firm relations creates a situat

transitions in the german labor market structure and crisis abstract since the so called hartz iv reforms around 2005 and during the global crisis of 2008 2009 the german labor market featured mainly declining unemployment rates we develop a search and matching model with heterogeneous skills to explore the role of structural and cyclical policies for this performance calibrating unemployment benefits to approximate legislation before and after the reforms we find a large reduction in unemployment and its duration with the transition concluding after about three years during the crisis the extended use of short time labor subsidies that prevent jobs from being destroyed is likely to have prevented strong increases in unemployment

information capacity and innovation adoption researchers of innovation adoption and diffusion often have tested the hypothesis that firms with greater capacities to gather and evaluate information should adopt sooner however the data generally do not support this hypothesis a theoretical model of innovation adoption under uncertainty is developed to show that greater information capacity implies not only faster learning which tends to reduce the expected delay until adoption but also a more stringent adoption criterion which tends to increase the expected delay the resulting ambiguity provides an explanation for the lack of empirical support for this hypothesis

strategic timing of adoption of new technologies under uncertainty abstract in this paper we introduce experience effects into a duopoly game of timing of adoption of new technologies which exhibit exogenous technological progress departing from the existing literature with this model we obtain continuous and downward sloping reaction functions we find that a higher level of uncertainty increases the extent of dispersion between the equilibrium timings of adoption furthermore we find that the equilibrium timings are even more dispersed when the leader takes the follower s reaction into account when firm roles are made endogenous we find that if there is an incentive to lead follow the equilibrium timings are more less dispersed finally we show that it is possible for collusive adoption to improve welfare

understanding unemployment flows this article reviews the current state of research on unemployment dynamics in macroeconomic models in particular it discusses the increasingly widespread use of the labour market flow approach as implemented via a search and matching process and presents main policy considerations that arise from this approach related to unemployment benefit systems and employment protection it reviews the implications of the labour flow approach for dynamic properties of macroeconomic models and discusses policy implications for macroeconomic and labour market policies finally it presents new evidence on the effectiveness of policies to influence unemployment in and outflows copyright 2011 oxford university press

technology policy interaction in frictional labour markets does capital embodied technological change play an important role in shaping labour market outcomes to address this question we develop a model with vintage capital and search matching frictions where irreversible investment in new vintages of capital creates heterogeneity in productivity among firms matched as well as vacant we demonstrate that capital embodied technological change reduces labour demand and raises equilibrium unemployment and unemployment durations in addition the presence of labour market regulations unemployment benefits payroll taxes and firing costs exacerbates these effects thus the model is qualitatively consistent with some key features of the european labour market experience relative to that of the u s it features a sharper rise in unemployment and a sharper fall in the vacancy rate and the labour share a calibrated version of our model suggests that this technology policy interaction could explain a sizeable fraction of the observed differences between the u s and europe copyright 2007 wiley blackwell

adoption and diffusion of an innovation of uncertain profitability the argument has frequently been made that the pattern of diffusion associated with most new innovations will typically have certain characteristics a diffusion curve for an innovation is usually defined as the proportion of its potential users who have already adopted as a function of time measured from the first adoption many empirical studies by both economists and other social scientists have shown that diffusion curves nearly always have two distinct characteristics i they are s shaped the proportion adopted is an increasing function of time which is initially convex but eventually becomes concave and ii they tend to be right hand skewed the inflection point occurs at a time corresponding to a proportion adopted which is less than one half so that the function is concave over the greatest amount of time in fact this skewing is occasionally severe enough to make the diffusion curve appear concave everywhere the focus of most empirical studies of innovation diffusion has centered on identification of either the major determinants of the speed of diffusion or the characteristics of firms which determine how long they delay adoption the seminal contributions are griliches 6 study of hybrid corn and mansfield s 121 study of 12 industrial innovations these studies and most of the similar ones following conclude that diffusion is faster for innovations with higher profitability and that large firms tend to be the earliest adopters some studies e g mansfield 121 herregat 71 have attempted to ascertain

taxes transfers and employment in an incomplete markets model the consequences of increases in the scale of tax and transfer programs are assessed in the context of a model with idiosyncratic productivity shocks and incomplete markets the effects are contrasted with those obtained in a stand in household model featuring no idiosyncratic shocks and complete markets the main finding is that the impact on hours remains very large but the welfare consequences are very different the analysis also suggests that tax and transfer policies have large effects on average labor productivity via selection effects on employment

indivisible labor lotteries and equilibrium abstract this paper considers an economy where labor is indivisible and agents are identical although the discontinuity in labor supply at the individual level disappears as a result of aggregation it is shown that indivisible labor has strong consequences for the aggregate bahavior of the economy it is also shown that optimal allocations involve lotteries over employment and consumption

a three state model of worker flows in general equilibrium abstract we develop a simple model featuring search frictions and a nondegenerate labor supply decision along the extensive margin the model is a standard version of the neoclassical growth model with indivisible labor and idiosyncratic productivity shocks and frictions characterized by employment loss and employment opportunity arrival shocks we argue that it is able to account for the key features of observed labor market flows for reasonable parameter values persistent idiosyncratic productivity shocks play a key role in allowing the model to match the persistence of the employment and out of the labor force states found in individual labor market histories

search unemployment and age abstract we examine a search and matching model of the labor market with overlapping generations of workers in this model we focus on the effects of the finite lifetime of workers as a result of finite lifetime very old workers with the same productivity as younger workers generally earn less a market solution with nash bargained wages is never optimal as old workers search too long compared to the efficient solution we also examine the effects of policy measures such as hiring subsidies or unemployment insurance on employment labor market institutions have a differential impact for different age groups

indivisible labor and the business cycle abstract a growth model with shocks to technology is studied labor is indivisible so all variability in hours worked is due to fluctuations in the number employed we find that unlike previous equilibrium models of the business cycle this economy displays large fluctuations in hours worked and relatively small fluctuations in productivity this finding is independent of individuals willingness to substitute leisure across time this and other findings are the result of studying and comparing summary statistics describing this economy an economy with divisible labor and post war u s time series

the role of shocks and institutions in the rise of european unemployment the aggregate evidence two key facts about european unemployment must be explained the rise in unemployment since the 1960s and the heterogeneity of individual country experiences while adverse shocks can potentially explain much of the rise in unemployment there is insufficient heterogeneity in these shocks to explain cross country differences alternatively while explanations focusing on labour market institutions explain current heterogeneity well many of these institutions pre date the rise in unemployment based on a panel of institutions and shocks for 20 oecd nations since 1960 we find that the interaction between shocks and institutions is crucial to explaining both stylised facts

technological learning and labor market dynamics the search and matching model of the labor market fails to match two important business cycle facts i a high volatility of unemployment relative to that of labor productivity and ii a mild correlation between these two variables we address these shortcomings by focusing on the implementation process of technological innovation that is the empirical nding that new technologies are subject to a learning process we consider a novel source of business cycles namely uctuations in the ease or speed of technological learning and show that a search and matching model featuring such shocks can account for both facts moreover our model provides a new interpretation of news shocks discussed in the recent business cycle literature

earnings losses and labor mobility over the life cycle an extensive empirical literature has documented that workers with high tenure suffer large and persistent earnings losses when they get displaced we study the reasons behind these losses in a tractable search model with a life cycle dimension endogenous job mobility worker and match heterogeneity the model reconciles key characteristics of the u s labor market large average transition rates a large share of stable jobs and the earnings losses from displacement we decompose the earnings losses and find that only 50 result from skill losses endogenous reactions and selection account for the remainder our findings have important implications for the welfare costs of displacement and labor market policy

understanding european unemployment with a representative family model abstract a representative family model with indivisible labor and employment lotteries has no labor market frictions and complete markets nevertheless its aggregate responses to an increase in government supplied unemployment insurance ui and to an increase in microeconomic turbulence are qualitatively similar to those in two macromodels with labor market frictions and incomplete markets namely the matching and search island models in ljungqvist and sargent 2007a understanding european unemployment with matching and search island models journal of monetary economics this issue because there is no frictional unemployment in the representative family model an increase in employment protection ep decreases aggregate work because the representative family substitutes leisure for work an effect opposite to what occurs in matching and search island models heterogeneity among workers highlights the economy wide coordination in labor supply and consumption sharing that employment lotteries and complete markets achieve in the representative family model a high disutility of labor makes generous ui cause very low employment levels

a theory of quits and layoffs with efficient turnover this paper answers the efficient turnover literature s long silence regarding the quit layoff distinction treating quits as worker initiated separations and layoffs as firm initiated separations i establish that the existence of layoffs is compatible with optimizing workers and firms forming and dissolving employment matches to exploit all the gains from trade the efficient turnover approach is shown to be consistent with many empirical regularities that distinguish quits from layoffs structural implications of the model are tested on data from the psid

european unemployment and turbulence revisited in a matching model we recalibrate den haan haefke and ramey s matching model to incorporate our preferred specie cation of turbulence as causing distinct dynamics of human capital after voluntary and involuntary job losses under our calibration with high unemployment benee ts an increase in turbulence increases the unemployment rate and the duration of unemployment while leaving the ine ow rate into unemployment roughly unchanged mirroring features of european data in the 1980s and 1990s the essential issue is that den haan haefke and ramey specify that in turbulent times workers experiencing layoffs and quits are both subject to instantaneous skill losses while we restrict instantaneous skill losses to laid off workers jel e24 j64

on the quantitative importance of market completeness abstract this paper quantitatively compares allocations in calibrated large overlapping generations growth models that only differ in their market structures for insuring against aggregate risk the findings are that the equilibrium behavior of aggregate variables is very similar across all market structures there are only minor differences the ratio of the volatility of aggregate consumption relative to that of investment is higher in complete market economies due partly to the higher volatility of consumption of older people it was also found that the risk premia in complete markets economies is basically zero therefore we can conclude that we can for the most part abstract from the issue of whether there exist markets for aggregate risk

optimal redistribution a life cycle perspective abstract in this paper i characterize the optimal redistribution policy in a simple life cycle framework with both an intensive and an extensive margin of labor supply the extensive margin corresponds to the choice of a retirement age the optimal allocation cannot be implemented in a decentralized economy by a standard non linear income tax alone it can however be implemented by a history dependent social security system which redistributes resources across agents a calibration of the model to the u s economy reveals that the retirement age should optimally be sharply increasing in productivity and that implementing the optimal life cycle redistribution policy can generate large social welfare gains

unemployment responses to skill biased technology shocks the role of labour market policy do skill biased shocks that increase the spread of labour productivities interacting with different policy regimes explain the rise in unemployment in europe relative to the united states in the 1980s and 1990s the hypothesis is an implication of a version of the mortensen and pissarides 1994 model of equilibrium unemployment which allows for worker heterogeneity a calibrated version of the model implies that a similar unemployment increase would have occurred in the united states over this period given changes in relative productivity by education implied by observed wage changes had unemployment compensation and employment protection policies been at european levels

monetary shocks in a model with skill loss unemployment shows persistent and long lasting responses to nominal and real shocks standard real business cycle models with search frictions but a homogeneous labor force are able to generate some volatility and persistence but not enough to match the empirical evidence moreover empirical studies emphasize the importance of the heterogeneity of the unemployment pool to fully understand unemployment dynamics in particular in most european countries the incidence of long term unemployment is large and well known one of the possible causes consequences of long term unemployment is the skill deterioration of the unemployment pool in this paper we introduce the skill loss mechanism and therefore a heterogeneous labor force in a new keynesian framework with search frictions calibrating the model for the spanish economy we show that while the skill loss mechanism helps to explain the magnitude of the response of unemployment to monetary shocks it does not improve the performance of the homogeneous worker model in terms of the persistence of the response especially for short and long term unemployment

life cycle labor supply with human capital accumulation a dynamic model of labor supply under uncertainty with endogenous human capital accumulation is developed and estimated using 1968 81 panel study of income dynamics male panel data given a learning by doing technology for human capital investment and a translog utility function structural parameters for preferences and technology are estimated from the orthogonality conditions implied by the euler equations assuming rational expectations the parameter estimates conform to economic theory simulations of the model suggest that the intertemporal labor supply elasticity with endogenous wages will rise over the lifecycle producing different policy implications than typical models with exogenous wages and constant intertemporal elasticities copyright 1989 by economics department of the university of pennsylvania and the osaka university institute of social and economic research association

income and wealth heterogeneity in the macroeconomy how do movements in the distribution of income and wealth affect the macroeconomy we analyze this question using a calibrated version of the stochastic growth model with partially uninsurable idiosyncratic risk and movements in aggregate productivity our main finding is that in the stationary stochastic equilibrium the behavior of the macroeconomic aggregates can be almost perfectly described using only the mean of the wealth distribution this result is robust to substantial changes in both parameter values and model specification our benchmark model whose only difference from the representative agent framework is the existence of uninsurable idiosyncratic risk displays far less cross sectional dispersion and skewness in wealth than u s data however an extension that relies on a small amount of heterogeneity in thrift does succeed in replicating the key features of the wealth data furthermore this extension features aggregate time series that depart significantly from permanent income behavior

declining labor turnover and turbulence abstract the rate of job loss has been on a secular decline for the last four decades or longer changes in demographics or industry composition do not account for the trend this paper seeks to identify the possible sources of the decline using a simple search and matching model with two types of workers experienced and inexperienced where the former type faces a risk of skill loss during unemployment the calibrated model suggests that a higher risk of skill loss during unemployment results in a lower job separation rate because workers accept lower wages in exchange for job security various other potential hypotheses are also examined

technology adoption decisions under irreversibility and uncertainty an ex ante appproach empirical results demonstrate that uncertainty about costs and requirements for environmental compliance is an important determinant of dairy producers investment behavior ex ante forecasting of how uncertainty and irreversibility are likely to affect producers responsiveness to agricultural technologies has implications for the design of environmental policies simulation modeling methods are described the empirical analysis focuses on texas producers propensity to adopt free stall dairy housing free stall investments offer advantages for both productivity augmentation and pollution abatement yet uncertainty and irreversibility are obstacles to adoption implications of this ex ante paradigm for policy design and implementation are discussed

turbulence and unemployment in a job matching model according to ljungqvist and sargent 1998 high european unemployment since the 1980s can be explained by a rise in economic turbulence leading to greater numbers of unemployed workers with obsolete skills these workers refuse new jobs due to high unemployment benefits in this paper we reassess the turbulence unemployment relationship using a matching model with endogenous job destruction in our model higher turbulence reduces the incentives of employed workers to leave their jobs if turbulence has only a tiny effect on the skills of workers experiencing endogenous separation then the results of ljungqvist and sargent 1998 2004 are reversed and higher turbulence leads to a reduction in unemployment thus changes in turbulence cannot provide an explanation for european unemployment that reconciles the incentives of both unemployed and employed workers jel e24 j64

prosperity and depression prosperity and depression are relative concepts today both france and japan are depressed relative to the united states equivalently the united states is prosperous relative to these countries i say these countries are depressed relative to the united states because their output per working age person is 30 percent less than the u s level an interesting and important policy question is why are these countries depressed the answers for these two countries turn out to be very different the united states is prosperous relative to france because the u s intratemporal tax wedge that distorts the trade off between consumption and leisure is much smaller than the french wedge i will show that if france modified its intratemporal tax wedge so that its value was the same as the u s value french welfare in consumption equivalents would increase by 19 percent consumption would have to increase by 19 percent now and in all future periods to achieve as large a welfare gain as that resulting from this tax reform the united states is prosperous relative to japan because production efficiency is higher in the united states in the united states total factor productivity is approximately 20 percent higher than in japan if japan suddenly became as efficient in production as the united states its welfare gain in consumption equivalents would be 39 percent equally interesting and important are big changes over time in relative output per working age person across countries why are new zealand s and switzerland s economies depressed by over 30 percent relative to their 1970 trend corrected levels both of these countries have small populations but depressions are not restricted to small countries japan with its 125 million people is now depressed by 20 percent relative to its 1991 trend corrected level on the prosperity side why are ireland and south korea so prosperous now relative to their 1970 trend corrected levels this lecture is concerned primarily with big international differences among relatively rich industrial countries and changes in these differences over time the countries that receive primary attention all have market economies and healthy well educated populations in the countries considered the variations in aggregate output per working age person are large and reasonably good measures of the factor inputs are available this permits in many cases the identification of the change in policy or the difference in policy that gave rise to prosperity or depression this is in contrast to business cycle theory which provides little guidance to policy except for the important policy implication that a stabilization effort will have either no effect or a perverse effect the output variations studied and analyzed in this lecture are big an order of magnitude larger than the much studied business cycle fluctuations the variations studied however are an order of magnitude smaller than the muchstudied differences between the richest and poorest countries surprisingly only recently have depressions been systematically studied from the perspective of growth theory which is the theory used university of minnesota and federal reserve bank of minneapolis i thank my colleagues at the university of minnesota and the federal reserve bank of minneapolis for helpful discussions and comments in particular i thank tim kehoe ellen mcgrattan and nancy stokey for their help i also thank martin weale and franck portier for providing some british and french tax information used in this lecture thanks also go to sami alpanda and james macgee for research assistance and helpful discussions this lecture draws heavily on collaborative research with fumio hayashi i thank the economic and social research institute cabinet office government of japan and the u s national science foundation for financial support the views expressed herein are those of the author and not necessarily those of the federal reserve bank of minneapolis or the federal reserve system

distributional dynamics following a technological revolution in this paper we explore the link between technological change and the dynamics of employment production and the distribution of earnings technological change not only advances society s collective capability but also changes the relative productivities of its members the latter effect establishes the likely winners and losers from advances in productive capabilities provides a mechanism that can generate cyclical fluctuations in output as well as employment and determines the evolution of the earnings distribution dynamique de la repartition a la suite d une revolution technologique ce memoire examine le lien entre le changement technologique et la dynamique de l emploi de la production et de la repartition des revenus le changement technologique n augmente pas seulement la capacite collective d une societe mais modifie aussi les productivites relatives de ses membres ce dernier effet cree des gagnants et des perdants declenche un mecanisme qui peut generer des fluctuations cycliques tant dans le niveau de production que dans celui de l emploi et determine l evolution de la repartition des revenus

does child labour displace schooling evidence on behavioral responses to an enrollment subsidy this brief summarizes the results of a gender impact evaluation study entitled does child labour displace schooling evidence on behavioral responses to an enrollment subsidy conducted between 1995 and 1996 in bangladesh the study observed that the subsidy increases schooling but its effect on child labour is ambiguous the subsidy increased schooling by far more than it reduced child labour substitution effects helped protect current incomes from the higher school attendance induced by the subsidy substitution effects helped protect current incomes from the higher school attendance induced by the subsidy the reduction in the incidence of child labour by boys girls represents about one quarter eighth of the increase in their school enrollment rate

worker flows job flows and unemployment in a matching model abstract standard matching models of unemployment generate far too little volatility in unemployment and vacancies relative to the variation in the shock variables shimer 2005 showed that in us data the vacancy to unemployment ratio is about 26 times more volatile than the standard model predicts he identified the flexibility of wages as the key issue and triggered a heated debate on possible improvements of the core model to accommodate these empirical facts in this paper we first document shimer s facts for the uk and find them to be qualitatively similar to us facts we then develop and calibrate a model based on the mortensen and pissarides approach that increases the volatility of the v u ratio 20 fold compared to the standard framework the key features of our model relate to the job creation decision by firms and the search options of workers we allow these to search whilst employed and firms to re advertise jobs that have been quit from this leads us to use a different job creation process whereby potential vacancies or job ideas arise at a finite rate per period over a range of idiosyncratic productivities calibrating the model to uk data we show that it delivers volatility in unemployment and vacancies much closer to though still not as large as that observed for the uk whilst retaining the standard wage determination process

aggregate implications of indivisible labor incomplete markets and labor market frictions this paper analyzes a model that features frictions an operative labor supply margin and incomplete markets we flrst provide analytic solutions to a benchmark model that includes indivisible labor and incomplete markets in the absence of trading frictions we show that the steady state levels of aggregate hours and aggregate capital stock are identical to those obtained in the economy with employment lotteries while individual employment and asset dynamics can be difierent second we introduce labor market frictions to the benchmark model we flnd that the efiect of the frictions on the response of aggregate hours to a permanent tax change is highly non linear we also flnd that there is considerable scope for substitution between voluntary and frictional nonemployment in some situations

optimal timing of technology adoption abstract in a dynamic programming framework this paper investigates the optimal timing of technology adoption by a competitive firm when technology choice is irreversible and the firm faces a stochastic innovation process with uncertainties about both the speed of the arrival and the degree of improvement of new technologies a numerical example illustrates how the optimal timing decision is affected by changes in parameter values reflecting market conditions the firm s initial technological attributes and the characteristics of the stochastic innovation process some of these effects turn out to be in sharp contrast to common intuition contrasting the optimal decision rule derived here with the rule obtained under the net present value shows that the former implies a slower pace of adoption than implied by the latter the optimal decision rule is generalized for the case of multiple technology switches and it is shown that for all the switching decisions except the last one the optimal rule satisfies the net present value criterion

the diffusion of new technology and the market for an innovation this article shows that the diffusion of a capital embodied process innovation results from a pattern of decreasing incremental benefits and adoption costs for later adoptions strategic behavior is inessential to this finding we develop a method for comparing diffusion rates for different market structures in the capital equipment market we consider cases with market power on the seller s side of the market and on the buyers side of the market a case with no market power and the welfare optimal case we find that a joint venture adopts an innovation more slowly than other market regimes to protect existing capital investments and that the adoption rate is slower than is socially optimal a monopoly supplier on the other hand adopts at a rate faster than is socially optimal this result is usually also the case when there is no market power finally we show that the monopoly supplier accelerates adoptions faster than in the case where there is no market power but retards later adoptions market power thus makes a difference in diffusion rates and on which side of the market that power lies makes a considerable difference

on the diffusion of new technology a game theoretic approach this paper is an attempt at a rigorous albeit not exceedingly general analysis of the diffusion of new technology in particular consider an industry composed of two firms each using the current best practice technology the firms are assumed to be operating at nash equilibrium output levels generating a market price given demand and profit allocations when a cost reducing innovation is announced each firm must determine when if ever to adopt it based in part upon the discounted cost of implementing the new technology and in part upon the behavior of the rival firm if either firm adopts before the other it can expect to make substantial profits at the expense of the other firm on the other hand the discounted sum of purchase price and adjustment costs may decline with the lengthening of the adjustment period as various quasi fixed factors become more easily variable therefore although waiting costs the firm more in terms of foregone profits it may save money on the cost of purchasing the new technology thus the firm must weigh the costs and benefits of delaying adoption as well as take account of its rival s strategic behavior

two questions about european unemployment a general equilibrium search model makes layoff costs affect the aggregate unemployment rate in ways that depend on equilibrium proportions of frictional and structural unemployment that in turn depend on the generosity of government unemployment benefits and skill losses among newly displaced workers the model explains how before the 1970s lower flows into unemployment gave europe lower unemployment rates than the united states and also how after 1980 higher durations have kept unemployment rates in europe persistently higher than in the united states these outcomes arise from the way europe s higher firing costs and more generous unemployment compensation make its unemployment rate respond to bigger skill losses among newly displaced workers those bigger skill losses also explain why u s workers have experienced more earnings volatility since 1980 and why especially among older workers hazard rates of gaining employment in europe now fall sharply with increases in the duration of unemployment

the horizontally s shaped laffer curve in a neoclassical growth model with incomplete markets and heterogeneous liquidity constrained agents the properties of the laffer curve depend on whether debt or transfers are adjusted to balance the government budget constraint the laffer curve conditional on public debt is horizontally s shaped two opposing forces explain this result first when government wealth increases the fiscal burden declines calling for lower tax rates second because the interest rate decreases when government wealth increases fiscal revenues may also decline calling for higher taxes for sufficiently negative government debt the second force dominates leading to the odd shape of the laffer curve conditional on debt

preemption and rent equalization in the adoption of new technology we study the adoption of a new technology to illustrate the effects of preemption in games of timing we show that the threat of preemption equalizes rents in a duopoly but that this result does not extend to the general oligopoly game if the gain to preemption is sufficiently small then the optimal symmetric outcome which involves late adoption is an equilibrium this contrasts with reinganum s result that in precommitment equilibria there must be diffusion we develop a new and richer formalism for modeling games of timing which permits a continuoustime representation of the limit of discrete time mixed strategy equilibria

technological acceleration skill transferability and the rise in residual inequality this paper provides a quantitative theory for the recent rise in residual wage inequality consistent with the empirical observation that a sizable part of this increase has a transitory nature a feature that eludes standard models based on ex ante heterogeneity in ability an acceleration in the rate of quality improvement of equipment like the one observed from the early 1970s increases the productivity quality differentials across machines jobs in a frictional labor market this force translates into higher wage dispersion even among ex ante equal workers with vintage human capital the acceleration reduces workers capacity to transfer skills from old to new machines generating a rise in the cross sectional variance of skills and therefore of wages through calibration the paper shows that this mechanism can account for 30 percent of the surge in residual inequality in the u s economy or for most of its transitory component two key implications of the theory faster within job wage growth and larger wage losses upon displacement find empirical support in the data

technological learning and labor market dynamics learning and labor market dynamics the search and matching model of the labor market fails to match two important business cycle facts i a high volatility of unemployment relative to labor productivity and ii a mild correlation between these two variables we address these shortcomings by focusing on technological learning by doing the notion that it takes workers time using a technology before reaching their full productive potential with it we consider a novel source of business cycles namely fluctuations in the speed of technological learning and show that a search and matching model featuring such shocks can account for both facts moreover our model provides a new interpretation of recently discussed news shocks

unemployment history and frictional wage dispersion abstract recent evidence shows that baseline search models struggle to match the observed levels of wage dispersion this paper studies a random matching search model with human capital losses during unemployment wage dispersion increases as workers accept lower wages to avoid long unemployment spells the model explains between a third and half of the observed residual wage dispersion when adding on the job search the model accounts for all of the residual wage dispersion and generates substantial dispersion even for high values of non market time the paper thus addresses the trade off between explaining frictional wage dispersion and the cyclical behavior of unemployment