gender wage gaps reconsidered a structural approach using matched employer employee data in this paper we study the extent to which wage differentials between men and women can be explained by differences in productivity disparities in friction patterns segregation and wage discrimination for this purpose we propose an equilibrium search model that features rent splitting on the job search and two sided heterogeneity in productivity the model is estimated using german matched employer employee data overall the results reveal that female workers are less productive and more mobile than males in addition female workers have on average slightly lower bargaining power than their male counterparts

substitute goods auctions and equilibrium this paper identifies two notions of substitutes for auction and equilibrium analysis weak substitutes the usual price theory notion guarantees monotonicity of t tonnement processes and convergence of clock auctions to a pseudo equilibrium but only strong substitutes which treats each unit traded as a distinct good with its own price guarantees that every pseudo equilibrium is a walrasian equilibrium that the vickrey outcome is in the core and that the law of aggregate demand is satisfied when goods are divisible weak substitutes along with concavity guarantees all of the above properties except for the law of aggregate demand

walrasian equilibrium with gross substitutes in this paper we study the problem of efficient production and allocation of indivisible objects among a set of consumers we assume that the agents preferences depend on the bundle of objects and the quantity of money they consume furthermore we assume that preferences are quasilinear in money and that agents have a large endowment of money with indivisibilities it is well known that many familiar properties of the utility functions fail to ensure existence in their striking analysis of the matching problem kelso and crawford 5 introduce the gross substitutes gs condition which ensures the non emptiness of the core we propose two new conditions and show that with quasilinearity they are equivalent article id jeth 1999 2531 available online at http www idealibrary com on

a quantitative evaluation of payroll tax subsidies for low wage workers an equilibrium search approach abstract phelps phelps e 1994 low wage employment subsidies versus the welfare state american economic review 84 54 58 presented the case for a low wage subsidy policy since the mid 1990s france has experimented with this strategy this paper evaluates the effect of this policy on employment and also on output and welfare we construct an equilibrium search model incorporating wage posting and specific human capital investment where unemployment and the distribution of both wages and productivity are endogenous we estimate this model using french data numerical simulations show that the prevailing minimum wage allows a high production level to be reached by increasing training investment even though the optimal minimum wage is lower we show that payroll tax subsidies enhance welfare more than a reduction in the minimum wage when they are spread over a large range of wages in order to avoid specialization in low productivity jobs

termination of dynamic contracts in an equilibrium labor market model i construct an equilibrium model of the labor market where workers and firms enter into dynamic contracts that can potentially last forever but are subject to optimal terminations upon a termination the firm hires a new worker and the worker who is terminated receives a termination contract from the firm and is then free to go back to the labor market to seek new employment opportunities and enter into new dynamic contracts the model permits only two types of equilibrium terminations that resemble respectively the two kinds of labor market separations that are typically observed in practice involuntary layos and voluntary retirements the model allows simultaneous determination of its equilibrium turnover unemployment and retirement as well as the expected utility of the new labor market entrants

the effects of immigration in frictional labor markets theory and empirical evidence from eu countries immigrants are new comers in a labor market as a consequence they lack of social networks and other country specific and not directly productive valuable assets affecting their relative bargaining position against employers we introduce this simple observation into a matching model of the labor market and show that immigrants increase employment prospects of competing natives to test the predictions of our model we exploit yearly vari ations between 1998 and 2004 in the share of immigrants within occupations of 12 european countries we identify the causal impact of immigrants on natives employment rate using an instrumental variable strategy based on historical settlement patterns across host countries and occupations by origin countries we find that natives employment rate increases in oc cupations and sectors receiving more immigrants moreover we highlight the heterogeneity of this impact across groups of immigrants and host countries along dimensions that affect immigrants natives relative reservation wages

credible threats in a wage bargaining model with on the job search abstract this note shows that in standard equilibrium search models with strategic wage bargaining and on the job search renegotiation does not require mutual consent if the worker needs a credible threat to trigger renegotiation wages are renegotiated less frequently than in the original model

sorting and the output loss due to search frictions we analyze a general search model with on the job search ojs and sorting of heterogeneous workers into heterogeneous jobs for given values of nonmarket time the relative efficiency of ojs and the amount of search frictions we derive a simple relationship between the unemployment rate mismatch and wage dispersion we estimate the latter two from standard micro data our methodology accounts for measurement error which is crucial to distinguish true from spurious mismatch and wage dispersion we find that without frictions output would be about 9 5 higher if firms can commit to pay wages as a function of match quality and 15 5 higher if they cannot noncommitment leads to a business stealing externality which causes a 5 5 drop in output

simultaneous auctions without complements are almost efficient abstract a simultaneous item auction is a simple procedure for allocating multiple indivisible goods to a set of bidders in a simultaneous auction every bidder submits bids on all items simultaneously the allocation and prices are then resolved for each item separately based solely on the bids submitted on that item such procedures are similar to auctions used in practice e g ebay but are not incentive compatible we study the efficiency of bayesian nash equilibrium bne outcomes of simultaneous first and second price auctions when bidders have complement free a k a subadditive valuations we show that the expected social welfare of any bne is at least 1 2 of the optimal social welfare in the case of first price auctions and at least 1 4 in the case of second price auctions

competitive equilibrium with indivisibilities abstract this paper studies an exchange economy with a finite number of agents in which each agents is initially endowed with a finite number of personalized indivisible commodities we observe that the equivalence theorem of the core and the competitive equilibrium may not hold for this economy when the coalitional form game is generated in the standard manner we provide an alternative definition of the coalitional form game to resolve this problem so that the balancedness of the new defined game provides a useful necessary and sufficient condition for the existence of competitive equilibrium for the original economy journal of economic literature classification numbers c71 d41 d51

on the job search sticky prices and persistence abstract models of the monetary transmission mechanism often generate empirically implausible business fluctuations this paper analyzes the role of on the job search in the propagation of monetary shocks in a sticky price model with labor market search frictions such frictions induce long term employment relationships such that the real marginal cost is determined by real wages and the cost of an employment relationship on the job search opens up an extra channel of employment growth that dampens the response of these two components because real marginal cost rigidity induces small price adjustments on the job search gives rise to a strong propagation of monetary shocks that increases output persistence

on the job search and moral hazard we analyze the interaction between intertemporal incentive contracts and search frictions associated with on the job search in our model agency problems call for wage contracts with deferred compensation at the same time workers do on the job search deferred compensation improves workers incentives to exert effort but distorts their on the job search decisions we show that deferred compensation is less attractive when the value to the worker firm pair of on the job search is high moreover the interplay between search frictions and wage contracts creates feedback effects if firms in equilibrium use contracts with deferred compensation fewer firms with vacancies enter the on the job search market and this in turn reduces the distortions created by deferred compensation these feedback effects between the incentive contracts used and the activity level in the search markets can lead to multiple equilibria a low turnover equilibrium where firms use deferred compensation and a high turnover equilibrium where they do not furthermore the model predicts that firms are more likely to use deferred compensation when search frictions are high and when the gains from on the job search are small

wage differentials employer size and unemployment the unique equilibrium solution to a game in which a continuum of individual employers choose permanent wage offers and a continuum of workers search by sequentially sampling from the set of offers is characterized wage dispersion is a robust outcome provided that workers search while employed as well as when unemployed the unique nondegenerate equilibrium distribution of wage offers is constructed for three cases 1 identical workers and employers 2 identical employers and an atomless distribution of worker supply prices and 3 identical workers and an atomless distribution of job productivities copyright 1998 by economics department of the university of pennsylvania and the osaka university institute of social and economic research association

the average shadow price for milps with integral resource availability and its relationship to the marginal unit shadow price abstract the economic significance of the average shadow price for integer and mixed integer linear programming milp problems has been established by researchers kim and cho eur j operat res 37 1988 328 crema eur j operat res 85 1995 625 in this paper we introduce a valid shadow price aspira for integer programs where the right hand side resource availability can only be varied in discrete steps we also introduce the concept of marginal unit shadow price musp we show that for integer programs a sufficient condition for the marginal unit shadow price to equal the average shadow price is that the law of diminishing returns should hold the polyhedral structures that will guarantee this equivalence have been explored identification of the problem classes for which the equivalence holds complements the existing procedure for determining shadow price for such integer programs the concepts of aspira and musp introduced in this paper can play a vital role in resource acquisition plans and in defining efficient market clearing prices in the presence of indivisibilities

price dispersion with directed search we model a market where identical buyers direct their search to identical capacity constrained sellers sellers cannot fully commit to the list price so strategic bargaining may determine the sale price we study search and pricing behavior in symmetric equilibrium sale prices exhibit equilibrium dispersion as they respond naturally to local demand conditions uncoordinated search decisions lead to equilibrium demand heterogeneity so sellers realizing large demand bargain prices up we characterize the sale price distribution parametrically studying how different commitment limitations and market features affect pricing and surplus shares we also determine endogenously

an efficient dynamic auction for heterogeneous commodities this paper proposes a new dynamic design for auctioning multiple heterogeneous commodities generalizing earlier work that treated identical objects an auctioneer wishes to allocate one or more units of each of k heterogeneous commodities to n bidders the auctioneer announces a vector of current prices bidders report back quantities demanded at these prices and the auctioneer adjusts the prices units are credited to bidders at the current prices as their opponents demands decline and the process continues until every commodity market clears bidders rather than being required to behave as price takers are permitted to strategically exercise their market power nevertheless with pure private values the proposed auction yields walrasian equilibrium prices an efficient outcome results as from a vickrey clarke groves mechanism but bidders are only required to evaluate their demands along a one dimensional path of prices rather than reporting their utilities over the entire k dimensional consumption set the auction is also more transparent and potentially simpler for bidders to understand and has the advantage of assuring the privacy of the upper portions of bidders demands theoretically the new auction provides a new foundation for convergence to walrasian equilibrium in an exchange economy practically it provides an efficient method for simultaneously auctioning two or more related types of securities for example three month and six month treasury bills it is also potentially useful for auctioning multiple types of communications spectrum for example licenses for paired and unpaired spectrum

stability and competitive equilibrium in trading networks we introduce a model in which agents in a network can trade via bilateral contracts we find that when continuous transfers are allowed and utilities are quasi linear the full substitutability of preferences is sufficient to guarantee the existence of stable outcomes for any underlying network structure furthermore the set of stable outcomes is essentially equivalent to the set of competitive equilibria and all stable outcomes are in the core and are efficient by contrast for any domain of preferences strictly larger than that of full substitutability the existence of stable outcomes and competitive equilibria cannot be guaranteed

the package assignment model we study assignment problems where individuals trade packages consisting of several rather than single objects although buyers reservations values are non additive efficient assignments can be formulated as a linear programming problem in which the pricing functions expressing duality may be non linear in the objects constituting the packages the interconnections among the linear programming formulation walrasian equilibrium and the core are established in the single seller auction version a necessary and sufficient condition is given for the vickrey payoff point to be implementable by a pricing equilibrium journal of economic literature classification numbers c62 d44 d51

learning your comparative advantages we introduce an equilibrium labor market model where workers gradually learn about their unobserved production abilities while engaged in a productive activity occupation workers observe their output and extract information that allows them to make inferences about their unobserved aptitudes because workers are learning about themselves their output informs them not only about their productivity in their current occupation but about their likely productivity in other occupations as well as workers acquire more information they self select into the occupations in which they expect to perform best and their wages increase returns to experience here capture improved job selection by workers as they sort through occupations and learn

auction protocols for decentralized scheduling decentralized scheduling is the problem of allocating resources to alternative possible uses over time where competing uses are represented by autonomous agents market mechanisms use prices derived through distributing bidding protocols to determine schedules we investigate the existence of equilibrium prices for some general classes of scheduling problems the quality of equilibrium solutions and the behavior of an ascending auction mechanism and bidding protocol to remedy the potential nonexistence of price equilibria due to complementarities in preference we introduce additional markets in combinations of basic goods finally we consider direct revelation mechanisms and compare to the market based approach journal of economic literature classification numbers c62 c70 d44

an efficient ascending bid auction for multiple objects when bidders exhibit multi unit demands standard auction methods generally yield inefficient outcomes this article proposes a new ascending bid auction for homogeneous goods such as treasury bills or telecommunications spectrum the auctioneer announces a price and bidders respond with quantities items are awarded at the current price whenever they are clinched and the price is incremented until the market clears with private values this dynamic auction yields the same outcome as the sealed bid vickrey auction but has advantages of simplicity and privacy preservation with interdependent values this auction may retain efficiency whereas the vickrey auction suffers from a generalized winner s curse

unhealthy insurance markets search frictions and the cost and quality of health insurance we analyze the effect of search frictions in the market for commercial health insurance frictions increase insurance premiums enough to transfer 13 2 percent of consumer surplus from fully insured employer groups to insurers approximately 34 4 billion in 1997 and increase insurance turnover by 64 percent for the average pol icy this rent transfer harms consumers and when combined with heightened turnover reduces incentives to invest in future health we also find that a publicly financed insurance option can improve the efficiency of private insurance markets by reducing search fric tion induced distortions in pricing and marketing efforts jel d83 g22 i18 in the united states health insurance for those under age 65 is typically provided through group plans purchased by employers from commercial insurers health insurance is a complex multi attribute service so employers looking to buy insur ance face a difficult shopping problem savvy purchasers must consider which of the many drugs their employees might use are in the insurer s formularies which local physicians are part of the insurer s provider network and what copays fees and deductibles apply to which pharmaceuticals providers and services comparison shopping is made even more difficult by the fact that many aspects of insurance involve commitments to provide services under hard to anticipate contingencies medical underwriting by insurers and the great profusion of insurance products raises administrative costs and increases the complexity of an employer group s

wage tenure contracts in a frictional labour market firms strategies for recruitment and retention a common assumption in equilibrium search and matching models of the labour market is that each firm posts a wage to be paid to any worker hired this paper considers the implications of firms posting contracts in a random matching model with on the job search more complex contracts enable firms to address both recruitment and retention problems by for example increasing the wage with tenure the effect on the labour market is to reduce turnover below the level required for efficient matching of workers to firms copyright 2004 wiley blackwell

on the job search mismatch and efficiency this paper characterizes the equilibrium for a large class of search models with two sided heterogeneity and on the job search besides the well known congestion externalities we show that on the job search in combination with monopsonistic wage setting without commitment creates a business stealing externality in the absence of congestion effects this leads to excessive vacancy creation under wage setting with commitment this externality is absent because when posting a wage firms take into account the expected productivity of future workers in their current jobs if firms are able to make and respond to counteroffers then they will not have to pay no quit premia and this also leads to excessive vacancy creation

job matching and coalition formation with utility or disutility of co workers abstract this paper studies the job matching market in kelso and crawford 1982 econometrica50 1483 1504 with one exception that co workers may generate utility or disutility in the workplace we provide a simple idea to show how a great number of sufficient conditions for a nonempty core in the literature can be extended to this labor market a generalized competitive equilibrium with a tax subsidy system is also discussed journal of economic literature classification number d71

competitive equilibria in two sided matching markets with general utility functions we present an exact characterization of utilities in competitive equilibria of two sided matching markets in which the utility of each agent depends on the choice of partner and the terms of the partnership potentially including monetary transfer examples of such markets include sellers and buyers or jobs and workers demange and gale showed that the set of competitive equilibria in this type of market forms a complete lattice with each extreme point of the lattice representing an equilibrium with the highest utilities for the agents on one side and the lowest utilities for the agents on the opposite side our characterization is based on establishing a connection between the competitive equilibria of a market and the competitive equilibria of certain strict subsets of that market each obtained by removing exactly one agent this characterization captures the effect of competition when agents are added to the market or removed from the market it gives a precise procedure for constructing competitive eq

technical efficiency market share and profitability of manufacturing firms in cote d ivoire the technology trap this paper investigates the sources of inefficiency of firms in cote d ivoire and exam ines to what extent these effects translate into poor performance a large majority of firms is technically inefficient producing far below the maximum attainable output level major cost savings can also be realised through enlarging the scale of activities of firms efficiency gains and scale advantages translate into a better competitive position and via their impact on market share into higher profitability however severe growth barriers and imperfect markets keep firms from realising these gains and prevent firms from catching up in technology with respect to their larger older and often foreign owned competitors

the existence and computation of competitive equilibria in markets with an indivisible commodity abstract this paper considers an exchange economy called a generalized assignment market in which sellers and buyers trade one indivisible commodity possibly with product differentiation for a perfectly divisible commodity the existence of a competitive equilibrium in this economy is proved using kakutani s fixed point theorem this existence theorem is applied to a production economy in which sellers are formulated as producers with convex cost functions two examples of housing markets are provided and their competitive equilibria are numerically calculated

the communication requirements of social choice rules and supporting budget sets the paper examines the communication requirements of social choice rules when the sincere agents privately know their preferences it shows that for a large class of choice rules any minimally informative way to verify that a given alternative is in the choice rule is by verifying a budget equilibrium i e that the alternative is optimal to each agent within a budget set given to him therefore any communication mechanism realizing the choice rule must find a supporting budget equilibrium we characterize the class of choice rules that have this property furthermore for any rule from the class we characterize the minimally informative messages budget equilibria verifying it this characterization is used to identify the amount of communication needed to realize a choice rule measured with the number of transmitted bits or real variables applications include efficiency in convex economies exact or approximate surplus maximization in combinatorial auctions the core in indivisible good economies and stable many to one matchings

on the job search and cyclical unemployment crowding out vs vacancy effects incorporating on the job search otjs into a real business cycle model has been shown to increase the cyclical volatility of unemployment using a particularly simple model of otjs we show that the increased search of employed workers during expansions induces firms to open more vacancies but also crowds out unemployed workers in the job search resulting in an ambiguous overall effect on unemployment volatility we show analytically and numerically that the difference between the employer s share of the match surplus with an employed versus an unemployed job seeker determines the degree to which otjs increases unemployment volatility we use this result to re consider some related papers of otjs and explain the amplification of volatility they obtain finally we show that a plausible calibration of the otjs model allows us to reproduce most significant features of the us labor data

estimating incentive and welfare effects of nonstationary unemployment benefits the distribution of unemployment duration in our equilibrium matching model with spell dependent unemployment benefits displays time varying exit rates building on semi markov processes we translate these rates into an expression for the aggregate unemployment rate structural estimation using german microdata allows us to discuss the effects of an unemployment benefit reform hartz iv the reform reduced unemployment by less than 0 1 percentage points contrary to general beliefs the net wage for most skill and regional groups increased taking the insurance effect of unemployment benefits into account however the reform is welfare reducing for 76 of workers

competitive equilibrium in an exchange economy with indivisibilities abstract we analyze an exchange economy in which i all commodities except money are indivisible ii agents preferences can be described by a reservation value for each bundle of indivisible objects and iii all agents are price takers we obtain a necessary and sufficient condition under which market clearing prices exist implications for market mechanisms are discussed journal of economic literatureclassification numbers d51 c78

understanding preferences demand types and the existence of equilibrium with indivisibilities we propose new techniques for understanding agents valuations our classification into demand types incorporates existing definitions substitutes complements strong substitutes etc and permits new ones our unimodularity theorem generalises previous results about when competitive equilibrium exists for any set of agents whose valuations are all of a demand type for indivisible goods contrary to popular belief equilibrium is guaranteed for more classes of purely complements than of purely substitutes preferences our intersection count theorem checks equilibrium existence for combinations of agents with specific valuations by counting the intersection points of geometric objects applications include matching and coalition formation and the product mix auction introduced by the bank of england in response to the financial crisis

on the job search productivity shocks and the individual earnings process individual labor earnings observed in worker panel data have complex highly persistent dynamics we investigate the capacity of a structural job search model with i i d productivity shocks to replicate salient properties of these dynamics such as the covariance structure of earnings the evolution of individual earnings mean and variance with the duration of uninterrupted employment or the distribution of year to year earnings changes specifically we show within an otherwise standard job search model how the combined assumptions of on the job search and wage renegotiation by mutual consent act as a quantitatively plausible internal propagation mechanism of i i d productivity shocks into persistent wage shocks the model suggests that wage dynamics should be thought of as the outcome of a specific acceptance rejection scheme of i i d productivity shocks this offers an alternative to the conventional linear arma type approach to modelling earnings dynamics structural estimation of our model on a 12 year panel of highly educated british workers shows that our simple framework produces a dynamic earnings structure which is remarkably consistent with the data

crime and the labor market a search model with optimal contracts abstract this paper extends the pissarides pissarides christopher a equilibrium unemployment theory cambridge mit 2000 model of the labor market to include crime and punishment a la becker becker gary s crime and punishment an economic approach journal of political economy 76 1968 169 217 all workers irrespective of their labor force status can commit crimes and the employment contract is determined optimally the model is used to study analytically and quantitatively the effects of various labor market and crime policies for instance a more generous unemployment insurance system reduces the crime rate of the unemployed but its effect on the crime rate of the employed depends on job duration and jail sentences when the model is calibrated to u s data the overall effect is to decrease crime but is quantitatively small small wage subsidies reduce unemployment and crime rates of employed and unemployed workers and raise society s welfare hiring subsidies reduce unemployment but they can raise the crime rate of employed workers crime policies police technology and jail sentences affect crime rates significantly but have only negligible effects on the labor market

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

on the job search and strategic bargaining abstract this paper studies wage bargaining in a simple economy in which both employed and unemployed workers search for better jobs the axiomatic nash bargaining solution and standard strategic bargaining solutions are inapplicable because the set of feasible payoffs is nonconvex i instead develop a strategic model of wage bargaining between a single worker and firm that is applicable to such an environment i show that if workers and firms are homogeneous there are market equilibria with a continuous wage distribution in which identical firms bargain to different wages each of which is a subgame perfect equilibrium of the bargaining game if firms are heterogeneous i characterize market equilibria in which more productive firms pay higher wages i compare the quantitative predictions of this model with burdett and mortensen s 1998 wage differentials employer size and unemployment international economic review 39 257 273 wage posting model and argue that the bargaining model is theoretically more appealing along important dimensions

productivity growth on the job search and unemployment abstract the impact of long run productivity growth on unemployment is studied we incorporate disembodied technological progress and on the job search into the endogenous job separation model of mortensen and pissarides 1994 because we include on the job search faster growth reduces unemployment by decreasing job separation and inducing job creation the incorporation of on the job search substantially improves the ability of the mortensen and pissarides model to explain the effect of growth on labor market variables specifically our model generates not only an empirically consistent sign of the effect but also a larger impact of growth on unemployment than the standard matching model

multi item auctions a collection of items is to be distributed among several bidders and each bidder is to receive at most one item assuming that the bidders place some monetary value on each of the items it has been shown that there is a unique vector of equilibrium prices that is optimal in a suitable sense for the bidders in this paper we describe two dynamic auction mechanisms one achieves this equilibrium and the other approximates it to any desired degree of accuracy

pricing and allocation for quality differentiated online services we explore the problem of pricing and allocation of unique one time digital products in the form of data streams we look at the short term problem where the firm has a capacitated shared resource and multiple products or service levels we formulate the allocatively efficient generalized vickrey auction gva for our setting and point out the computational challenges in determining the individual discriminatory transfer payments we propose an alternative uniform price computationally efficient revenue maximizing knapsack formulation called the multiple vickrey auction mva while not incentive compatible the mva mechanism achieves bounded posterior regret and can be solved in real time it has the added benefit of realizing imputed commodity prices for the various services a feature lacking in the discriminatory gva approach for service providers that are concerned about the incentive compatibility but want imputed service prices we suggest a maximal mva mmva uniform pricing scheme that trades off revenue maximization for allocative efficiency for sake of completeness we discuss the properties of a first price pay your bid scheme while np hard and not incentive compatible this formulation has the perceived benefit of cognitive simplicity on the parts of sellers and bidders

bundling decisions by a multiproduct monopolist with incomplete information this paper analyzes bundling decisions of a rnultiproduct monopolist facing uncertain demand the monopolist sells his products using an auction mechanism and the market is analyzed as a game with incomplete information in which the buyers as well as the seller are strategic agents with a small number of buyers a profit maximizing seller will bundle all his output this makes buyers uniformly worse off compared to the case where the same monopolist does not bundle in the sense that any buyer is worse off regardless of his demand for the monopolist s outputs with a larger number of buyers the seller will have a tendency to unbundle his output and high demand buyers are worse off than they would be if the monopolist bundled his output low demand buyers on the other hand are always better off when the monopolist unbundles his output regardless of the number of competing buyers despite the fact that high demand buyers are the typical purchasers of the monopolist s output the net effect of increasing the number of buyers is greater market efficiency since bundling creates market inefficiencies both ex post and ex ante

identification of search models using record statistics this paper shows how record value theory a branch of statistics that deals with the timing and magnitude of extreme values in sequences of random variables can be used to recover features of the wage offer distribution in conventional search models using national longitudinal survey of youth nlsy wage data i show that the data are not compatible with specifications for the offer distribution characterized by extreme negative skewness in addition i show that my approach can be used to construct a bound on the returns to job seniority my results suggest that job seniority plays only a minor role in the wage growth of the workers surveyed in the nlsy copyright 2008 wiley blackwell

package auctions and exchanges we report recent advances concerning the package allocation problem in which traders seek to buy or sell combinations of goods the problems are most difficult when some goods are not substitutes in that case competitive equilibrium typically fail to exist but the core is non empty and comprises the competitive solutions also in that case the vickrey auction fails to select core allocations and yield revenues that are less than competitive the ausubel milgrom auction generally selects core allocations and when goods are substitutes prescribes the vickrey allocation we also evaluate the problems and promise of mechanisms for the package exchange problem

equilibrium wage tenure contracts in this study we consider a labor market matching model where firms post wage tenure contracts and workers both employed and unemployed search for new job opportunities given workers are risk averse we establish there is a unique equilibrium in the environment considered although firms in the market make different offers in equilibrium all post a wage tenure contract that implies a worker s wage increases smoothly with tenure at the firm as firms make different offers there is job turnover as employed workers move jobs as the opportunity arises this implies the increase in a worker s wage can be due to job to job movements as well as wage tenure effects further there is a nondegenerate equilibrium distribution of initial wage offers that is differentiable on its support except for a mass point at the lowest initial wage we also show that relevant characteristics of the equilibrium can be written as explicit functions of preferences and the other market parameters

labor search and matching in macroeconomics abstract the labor search and matching model plays a growing role in macroeconomic analysis this paper provides a critical selective survey of the literature four fundamental questions are explored how are unemployment job vacancies and employment determined as equilibrium phenomena what determines worker flows and transition rates from one labor market state to another how are wages determined what role do labor market dynamics play in explaining business cycles and growth the survey describes the basic model reviews its theoretical extensions and discusses its empirical applications in macroeconomics the model has been developed against the background of difficulties with the use of the neo classical frictionless model of the labor market in macroeconomics its success includes the modelling of labor market outcomes as equilibrium phenomena the reasonable fit of the data and when inserted into business cycle models improved performance of more general macroeconomic models at the same time there is evidence against the nash solution used for wage setting and an active debate as to the ability of the model to account for some of the cyclical facts

equilibria and indivisibilities gross substitutes and complements this paper examines an exchange economy with heterogeneous indivisible objects that can be substitutable or complementary we show that a competitive equilibrium exists in such economies provided that all the objects can be partitioned into two groups and from the viewpoint of each agent objects in the same group are substitutes and objects across the two groups are complements this condition generalizes the well known kelso crawford gross substitutes condition and is called gross substitutes and complements we also provide practical and typical examples from which substitutes and complements are both jointly observed

large firms and within firm occupational reallocation abstract this paper considers the equilibrium interaction between within firm and across firm reallocation in the presence of labor market frictions while a sizable literature has investigated frictional labor markets it has ignored within firm mobility nonetheless every year a sizable fraction of workers switch occupations without changing firms employees in large firms can sample from a larger selection and across firm mobility is replaced by within firm mobility bringing together within and across firm reallocation along with labor market frictions naturally accounts for the observed differences in worker flows and wages across firms of different sizes

informational limitations of ascending combinatorial auctions abstract we study the inherent limitations of natural widely used classes of ascending combinatorial auctions specifically we show that ascending combinatorial auctions that do not use both non linear prices and personalized prices cannot achieve social efficiency with general bidder valuations we also show that the loss of efficiency can be severe and that only a diminishing fraction of the social welfare may be captured this justifies the added complexity in the auctions suggested by e g parkes and ungar 2000 29 and ausubel and milgrom 2002 2

connecting the cooperative and competitive structures of the multiple partners assignment game multiple partners assignment game is the name used by sotomayor the multiple partners game in m majumdar ed equilibrium and dynamics essays in honor of david gale the macmillan press ltd new york 1992 the lattice structure of the set of stable outcomes of the multiple partners assignment game int j game theory 28 1999 567 583 to describe the cooperative structure of the many to many matching market with additively separable utilities stability concept is proved to be different from the core concept an economic structure is proposed where the concept of competitive equilibrium payoff is introduced in connection to the equilibrium concept from standard microeconomic theory the paper examines how this equilibrium concept compares with the cooperative equilibrium concept properties of interest to the cooperative and competitive markets are derived

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