are health insurance markets competitive to gauge the competitiveness of the group health insurance industry i investigate whether health insurers charge higher premiums ceteris paribus to more profitable firms such direct price discrimination is feasible only in imperfectly competitive settings using a proprietary national database of health plans offered by a sample of large multisite firms from 1998 2005 i find firms with positive profit shocks subsequently face higher premium growth even for the same health plans moreover within a given firm those sites located in concentrated insurance markets experience the greatest premium increases the findings suggest health care insurers are exercising market power in an increasing number of geographic markets

behavioral hazard in health insurance a fundamental implication of standard moral hazard models is overuse of low value medical care because copays are lower than costs in these models the demand curve alone can be used to make welfare statements a fact relied on by much empirical work there is ample evidence though that people misuse care for a different reason mistakes or behavioral hazard much high value care is underused even when patient costs are low and some useless care is bought even when patients face the full cost in the presence of behavioral hazard welfare calculations using only the demand curve can be off by orders of magnitude or even be the wrong sign we derive optimal copay formulas that incorporate both moral and behavioral hazard providing a theoretical foundation for value based insurance design and a way to interpret behavioral nudges once behavioral hazard is taken into account health insurance can do more than just provide financial protection it can also improve health care efficiency jel codes d03 i12 i13 i30 i38

disaggregating the developing welfare state provincial social policy regimes in china summary local variation in social welfare provision appears in myriad contexts around the world and yet our attempts at conceptualizing welfare regimes focus on the national level in china local authorities have shaped social policy implementation since economic reforms in this paper i answer three questions about subnational variation in social policy provision in china 1 have chinese provinces diverged in their social policy provision 2 how do provincial social policy regimes differ from one another 3 what explains variation in provincial social policy spending to answer the first question i conduct a cluster analysis of provincial social policy spending data i find that provinces systematically diverge in their social policy priorities while some provinces invest in education to develop human capital and promote economic growth others emphasize poverty alleviation i propose a typology to conceptualize these tendencies i then test for these divergent approaches using between effects regression models of provincial social policy spending although provincial wealth and needs sometimes play a role in allocations for social policy i find that economic development strategy and social instability are associated with distinct approaches to social welfare spending these distinct provincial welfare regimes have implications for the adoption implementation and ultimately effectiveness of social policy in china

testing for asymmetric information in insurance markets the first goal of this paper is to provide a simple and general test of the presence of asymmetric information in contractual relationships within a competitive context we also argue that insurance data are particularly well suited to such empirical investigations to illustrate this claim we use data on contracts and accidents to investigate the extent of asymmetric information in the french market for automobile insurance using various parametric and nonparametric methods we find no evidence for the presence of asymmetric information in this market

belief based refinements in signalling games abstract there are many economic problems which when modelled as games of incomplete information give rise to many sequential equilibria severely limiting the usefulness of the model there has recently been a large literature devoted to refining the set of equilibria in order to reduce this multiplicity by restricting the set of admissible disequilibrium beliefs this paper argues that the logical foundations of some refinements and the equilibria they focus on are problematic and further proposes an alternative refinement that avoids the difficulties we also provide an existence theorem covering a broad class of signalling games often studied in economics journal of economic literature classification numbers c72 c70 d82

using elasticities to derive optimal income tax rates this paper derives optimal income tax formulas using compensated and uncompensated elasticities of earnings with respect to tax rates a simple formula for the high income optimal tax rate is obtained as a function of these elasticities and the thickness of the top tail of the income distribution in the general non linear income tax problem this method using elasticities shows precisely how the different economic effects come into play and which are the key relevant parameters in the optimal income tax formulas of mirrlees the optimal non linear tax rate formulas are expressed in terms of elasticities and the shape of the income distribution these formulas are implemented numerically using empirical earning distributions and a range of realistic elasticity parameters

selection in insurance markets theory and empirics in pictures government intervention in insurance markets is ubiquitous and the theoretical basis for such intervention based on classic work from the 1970s has been the problem of adverse selection over the last decade empirical work on selection in insurance markets has gained considerable momentum this research finds that adverse selection exists in some insurance markets but not in others and it has uncovered examples of markets that exhibit advantageous selection a phenomenon not considered by the original theory and one that has different consequences for equilibrium insurance allocation and optimal public policy than the classical case of adverse selection advantageous selection arises when the individuals who are willing to pay the most for insurance are those who are the most risk averse and so have the lowest expected cost indeed it is natural to think that in many instances individuals who value insurance more may also take action to lower their expected costs drive more carefully invest in preventive health care and so on researchers have taken steps toward estimating the welfare consequences of detected selection and of potential public policy interventions in this essay we present a graphical framework for analyzing both theoretical and empirical work on selection in insurance markets this graphical approach provides both a useful and intuitive depiction of the basic theory of selection and its implications for welfare and public policy as well as a lens through which one can understand the ideas and limitations of existing empirical work on this topic

the efficiency of competitive equilibria in insurance markets with asymmetric information abstract this paper addresses the relationship between competitive equilibria and efficient allocations in an insurance market with asymmetric information using the definition of second best efficiency proposed by harris and townsend 1981 for environments characterized by informational assmmetry the efficiency properties of several proposed market equilibria are examined we find an analogue to the first optimality theorem a miyazaki wilson equilibrium always results in a second best allocation

unemployed but optimistic optimal insurance design with biased beliefs biased perceptions of risks change the perceived value of insurance and the per ceived returns to avoiding these risks i show empirically that unemployed workers overestimate how quickly they will nd work but underestimate the return to their search eorts i analyze the consequences for the optimal design of unemployment insurance with biased beliefs contracts equalizing the marginal smoothing ben e t and the moral hazard cost of insurance are suboptimal social and private insurance diverge a paternalistic social planner corrects the moral hazard cost for the distortion in the insured s eort choice while private insurers focus on the perceived rather than the true smoothing bene ts when unemployed workers are optimistic privatizing unemployment insurance may result in ine ciently low or rapidly decreasing unemployment bene ts

state corroding federalism competition among local governments in a decentralized political system is often thought to discipline lazy or corrupt officials improving public good provision and increasing welfare some scholars note possible distortions due to spillovers or a race to the bottom but suggest that central transfers or regulations can remedy these both arguments take for granted a framework of constitutional order in which the central government can collect taxes allocate transfers and enforce regulations autonomously but what if it can t we show that if central enforcement capacity is endogenous interjurisdictional competition may itself erode the center s ability to channel competition in welfare enhancing directions regional governments may compete for capital by shielding firms from central tax collectors bankruptcy courts or regulators the equilibrium result is weaker central law enforcement and usually lower welfare interjurisdictional competition corrodes the state we illustrate with three examples from russia china and the us of cases in which such competition apparently encouraged subnational politicians to help firms evade central taxes or regulations

equilibria in health exchanges adverse selection versus reclassification risk this paper studies equilibrium and welfare in a class of regulated health insurance markets known as exchanges we use detailed health plan choice and utilization data to model individual level i projected health risk and ii risk preferences we combine the estimated distributions of risk and risk preferences with a model of competitive insurance markets to predict allocations and prices

multiple dimensions of private information evidence from the long term care insurance market we demonstrate the existence of multiple dimensions of private information in the long term care insurance market two types of people purchase insurance individuals with private information that they are high risk and individuals with private information that they have strong taste for insurance ex post the former are higher risk than insurance companies expect while the latter are lower risk in aggregate those with more insurance are not higher risk our results demonstrate that insurance markets may suffer from asymmetric information even absent a positive correlation between insurance coverage and risk occurrence the results also suggest a general test for asymmetric information

marshallian vs walrasian stability in an experimental market the experiments discussed below are an attempt to examine concepts of stability as found in economic textbooks two concepts of stability which stem from two different concepts of market adjustment seem to have dominated thinking whilst these two concepts are typically called walras stability and marshall stability some controversy exists over the extent to which these two models represent their respective thinking no doubt the current formal statements of the theories reflect an evolution of the ideas through the work of many theorists the terminology is retained for convenience regardless of their origins these two concepts lead to competing hypotheses about the conditions under which market instability will be observed so the subject is a natural one for experimental investigation furthermore since this is the first experimental examination of the stability of equilibria the strategy is to inquire about stability in the context of these two classical models and to avoid the temptation to attempt to extend them or integrate them with more modern theory the old models have not been checked they seem to be an appropriate place to start

general equilibrium with free entry a synthetic approach to the theory of perfect competition the purpose of this essay is to explain a new theory of perfect competition that synthesizes the arrow debreu mckenzie and marshallian theories and summarizes the recent work of a large number of researchers the synthetic theory provides a logically precise general equilibrium framework that can be used both for positive analysis as well as to form a basis for the classical theorems of welfare economics in these aspects it follows the adm theory however as in the marshallian theory there is free entry in the form of an unbounded pool of firms which have access to the existing technology also as in the marshallian theory the average cost curves available to each firm are u shaped in contrast to both the marshallian and the adm theories we do not take price taking as a hypothesis we use the term perfect competition to describe a situation in which firms are arbitrarily small relative to the markets in which they are involved the firms in our model correctly perceive the effect of the amount that they place on the market on prices and they act to maximize profit with this in mind perfectly competitive equilibria are defined as the limit points of equilibria as firms become small relative to the market and following cournot we observe that as firms become small their ability to influence price disappears a new condition is identified which is important for the viability of competitive markets loosely speaking this condition requires that prices provide the proper entry signals for firms if one thinks of each firm as associated with the use of an unpriced and nondivisible resource sometimes referred to as entrepreneurship then in equilibrium the returns to that factor must fall with entry and rise with exit not only the stability theorems of the synthetic theory but also the existence theorem reject the application of the competitive model to a regime in which entry drives up and exit reduces the profit of similar firms

asymmetric information in insurance general testable implications several recent articles on empirical contract theory and insurance have tested for a positive correlation between coverage and ex post risk as predicted by standard models of pure adverse selection or pure moral hazard we show here that the positive correlationproperty can be extended to general setups competitive insurance markets and cases where risk aversion is public we test our results on a french dataset our tests confirm that the estimated correlation is positive they also suggest the presence of market power

existence of optimal mechanisms in principal agent problems we provide general conditions under which principal agent problems with either one or multiple agents admit mechanisms that are optimal for the principal our results cover as special cases pure moral hazard and pure adverse selection we allow multidimensional types actions and signals as well as both financial and non financial rewards our results extend to situations in which there are ex ante or interim restrictions on the mechanism and allow the principal to have decisions in addition to choosing the agent s contract beyond measurability we require no a priori restrictions on the space of mechanisms it is not unusual for randomization to be necessary for optimality and so it should be and is permitted randomization also plays an essential role in our proof we also provide conditions under which some forms of randomization are unnecessary

nonlinear pricing with random participation the canonical selection contracting programme takes the agent s participation decision as deterministic and finds the optimal contract typically satisfying this constraint for the worst type upon weakening this assumption of known reservation values by introducing independent randomness into the agents outside options we find that some of the received wisdom from mechanism design and nonlinear pricing is not robust and the richer model which allows for stochastic participation affords a more general empirical specification we develop a multidimensional methodology for addressing this class of problems providing two important applications to nonlinear pricing first with nonlinear pricing by a monopolist the familiar nodistortion at the top result persists but in tandem with the surprising conclusion that there is either no distortion at the bottom or bunching second in a simple model of product differentiated duopolists competing with nonlinear pricing we show that generally the duopoly outcome is qualitatively similar to the monopoly outcome however when marginal costs are symmetric and competition is sufficiently intense distortions disappear and the equilibrium outcome takes a remarkably simple form efficient quality allocations with cost plus fee pricing

efficient competitive equilibria with adverse selection do walrasian markets function orderly in the presence of adverse selection in particular is their outcome efficient when exclusive contracts are enforceable this paper addresses these questions in the context of a rothschild stiglitz insurance economy we identify an externality associated with the presence of adverse selection as a special form of consumption externality consequently we show that competitive equilibria always exist but are not typically incentive efficient however as markets for pollution rights can internalize environmental externalities markets for consumption rights can be designed to internalize the consumption externality due to adverse selection with such markets competitive equilibria exist and incentive constrained versions of the first and second welfare theorems hold

health insurance for humans information frictions plan choice and consumer welfare traditional models of insurance choice are predicated on fully informed and rational consumers protecting themselves from exposure to financial risk in practice choosing an insurance plan is a complicated decision often made without full information in this paper we combine new administrative data on health plan choices and claims with unique survey data on consumer information to identify risk preferences information frictions and hassle costs our additional friction measures are important predictors of choices and meaningfully impact risk preference estimates we study the implications of counterfactual insurance allocations to illustrate the importance of distinguishing between these micro foundations for welfare analysis

selection on moral hazard in health insurance economic analysis of market failure in insurance markets tends to analyze selection and moral hazard as distinct phenomena in this paper we explore the potential for selection on moral hazard in insurance markets by this we mean the possibility that moral hazard effects are heterogenous across individuals and that individuals selection of insurance coverage is affected by their anticipated behavioral response to coverage we examine these issues empirically in the context of employer provided health insurance in the united states specifically we break down the general

non exclusive competition in the market for lemons in order to check the impact of the exclusivity regime on equilibrium allocations we set up a simple akerlof like model in which buyers may use arbitrary taris under exclusivity we obtain the zero profit separating riley rothschilds stiglitz allocation under non exclusivity there is also a unique equilibrium allocation that involves a unique price as in akerlof 1970 these results can be applied to insurance in the dual model in yaari 1987 and have consequences for empirical tests of the existence of asymmetric information

estimating welfare in insurance markets using variation in prices we provide a graphical illustration of how standard consumer and producer theory can be used to quantify the welfare loss associated with inefficient pricing in insurance markets with selection we then show how this welfare loss can be estimated empirically using identifying variation in the price of insurance such variation together with quantity data allows us to estimate the demand for insurance the same variation together with cost data allows us to estimate how insurers costs vary as market participants endogenously respond to price the slope of this estimated cost curve provides a direct test for both the existence and the nature of selection and the combination of demand and cost curves can be used to estimate welfare we illustrate our approach by applying it to data on employerprovided health insurance from one specific company we detect adverse selection but estimate that the quantitative welfare implications associated with inefficient pricing in our particular application are small in both absolute and relative terms

paying a premium on your premium consolidation in the us health insurance industry we examine whether and to what extent consolidation in the u s health insurance industry is leading to higher employer sponsored insurance premiums we make use of a proprietary panel dataset of employer sponsored healthplans enrolling over 10 million americans annually between 1998 and 2006 to explore the relationship between premium growth and changes in market concentration we exploit the differential impact of a large national merger of two insurance firms across local markets to estimate the causal effect of concentration on market level premiums we estimate real premiums increased by approximately 7 percentage points in a typical market due to the rise in concentration during our study period we also find evidence that consolidation facilitates the exercise of monopsonistic power vis a vis physicians whose absolute employment and relative earnings decline in its wake

pareto optima and competitive equilibria with adverse selection and moral hazard this paper explores the extent to which standard general equilibrium analysis of pareto optima and of competitive equilibria can be applied to environments with moral hazard and adverse selection problems allowing for lotteries contracts with random components we first establish that an adverse selection insurance economy a moral hazard insurance economy a signaling economy and a private information labor market economy are all special cases of a simple general structure we then show that techniques for characterizing pareto optimal contracts as solutions to concave programming problems are useful and nice and appear to be broadly applicable allowing for lotteries we show how to characterize the optimal allocations for the adverse selection insurance and labor market economies we then show that standard existence and optimality theorems for competitive equilibria apply in the linear space containing lotteries if agents with characteristics which are distinct and privately observed at the time of initial trading enter the economy wide resource constraints in a homogeneous way other kinds of diversity are not critical for economies with moral hazard which satisfy the homogeneity condition competitive contract markets single out a subset of the optima and thus can be consistent with apparent unemployment and with a random allocation of labor supplied though all households are averse to risk the adverse selection insurance and signaling economies however do not satisfy the homogeneity condition and are difficult to decentralize efficiently with a price system

a complete solution to a class of principal agent problems with an application to the control of a self managed firm this paper considers a class of principal agent problems which have the following features 1 there is adverse selection because the principal ignores the value of one parameter of the agent s true characteristics 2 leaving aside the information parameter the principal s welfare as well as the agent s welfare depend on two types of variables observable to both of them the first ones possibly multidimensional are called action variable s and the second one which is one dimensional has in general the meaning of a money transfer 3 the principal is a stackelberg leader of the two person game he can commit himself to decision rules which are admissible on informational grounds he optimizes within the adequate class taking into account besides the agent s reaction one constraint which has generally the meaning of an individual rationality constraint and sometimes of a feasibility constraint the optimization is limited to the class of non stochastic mechanisms 4 the problem can also receive an alternative interpretation the principal faces a continuum of agents of unknown characteristics the distribution being known however stylized principal agent problems of this type have often been considered in the economic literature in particular the reader will later be able to recognize that the standard income tax model a la mirrlees 1971 the quality or quantity choice model of the monopolist a la mussa and rosen 1978 or maskin and riley 1982 and the model of government regulation of the private monopolist of baron and myerson 1982 all belong to

perfect competition in markets with adverse selection this paper proposes a perfectly competitive model of a market with adverse selection prices are determined by zero profit conditions and the set of traded contracts is determined by free entry crucially for applications contract characteristics are endogenously determined consumers may have multiple dimensions of private information and an equilibrium always exists equilibrium corresponds to the limit of a differentiated products bertrand game we apply the model to establish theoretical results on the equilibrium effects of mandates mandates can increase efficiency but have unintended consequences with adverse selection an insurance mandate reduces the price of low coverage policies which necessarily has indirect effects such as increasing adverse selection on the intensive margin and causing some consumers to purchase less coverage

optimal mandates and the welfare cost of asymmetric information evidence from the u k annuity market much of the extensive empirical literature on insurance markets has focused on whether adverse selection can be detected once detected however there has been little attempt to quantify its welfare cost or to assess whether and what potential government interventions may reduce these costs to do so we develop a model of annuity contract choice and estimate it using data from the u k annuity market the model allows for private information about mortality risk as well as heterogeneity in preferences over different contract options we focus on the choice of length of guarantee among individuals who are required to buy annuities the results suggest that asymmetric information along the guarantee margin reduces welfare relative to a first best symmetric information benchmark by about 127 million per year or about 2 percent of annuitized wealth we also find that by requiring that individuals choose the longest guarantee period allowed mandates could achieve the first best allocation however we estimate that other mandated guarantee lengths would have detrimental effects on welfare since determining the optimal mandate is empirically difficult our findings suggest that achieving welfare gains through mandatory social insurance may be harder in practice than simple theory may suggest

competitive pooling rothschild stiglitz reconsidered we build a model of competitive pooling which incorporates adverse selection and signaling into general equilibrium pools are characterized by their quantity limits on contributions households signal their reliability by choosing which pool to join in equilibrium pools with lower quantity limits sell for a higher price even though each household s deliveries are the same at all pools the rothschild stiglitz model of insurance is included as a special case we show that by recasting their hybrid oligopolistic competitive story in our perfectly competitive framework their separating equilibrium always exists even when they say it does not and is unique

electoral competition globalization and subnational education spending in mexico 1999 2004 this article examines the determinants of primary education spending among 29 mexican states from 1999 to 2004 there is wide variation in spending despite expectations of policy convergence due to market forces associated with globalization and in spite of the unique potential of education spending to complement economic strategies in achieving equitable growth this study exploits significant advantages of subnational analysis in exploring political and economic variables that have been useful in explaining spending levels cross nationally consistent with these studies this article shows that greater electoral competition leads to increased spending in contrast to other work however this study finds that exposure to the global economy has distinctly mixed effects on education spending these findings thus further highlight the positive returns to higher quality democracy while underscoring the need to examine the effects of many different aspects of globalization representing a wide variety of strategies employed by governments in engaging the international economy

how does risk selection respond to risk adjustment new evidence from the medicare advantage program to combat adverse selection governments increasingly base payments to health plans and providers on enrollees scores from risk adjustment formulae in 2004 medicare began to risk adjust capitation payments to private medicare advantage ma plans to reduce selection driven overpayments but because the variance of medical costs increases with the predicted mean incentivizing enrollment of individuals with higher scores can increase the scope for enrolling overpriced individuals with costs significantly below the formula s prediction indeed after risk adjustment ma plans enrolled individuals with higher scores but lower costs conditional on their score we find no evidence that overpayments were on net reduced

insurer pricing and consumer welfare evidence from medigap this article examines the welfare impact of imperfect competition in the medicare supplement insurance medigap market two firms control nearly three fourths of the medigap market and premiums exceed claims by over 25 i find that a low price elasticity and consumers brand preferences lead firms to engage in substantial marketing and price above cost therefore the strategic behavior of insurers facing relatively inelastic demand is critical in explaining poor market performance i also find that insurers do not capture all of the rents in this market rents also accrue to actors who perform marketing functions including agents and brokers

optimal risk adjustment in markets with adverse selection an application to managed care it is well known that adverse selection causes distortions in contracts in markets with asymmetric information taxing inefficient contracts and subsidizing the efficient ones can improve market outcomes bruce c greenwald and joseph e stiglitz 1986 although regulators rarely seem to implement tax and subsidy schemes with adverse selection motives in mind contracts are often complex and incomplete and it is the inefficient elements of the contract that are difficult to verify and hence tax or subsidize this is precisely the reason that in health insurance markets rather than subsidizing contracts regulators and payers contend with adverse selection by taxing and subsidizing the price paid to insuring health plans on the basis of observable characteristics of the persons joining the plan a practice known as risk adjustment risk adjusted premiums are paid to managed care plans plans that ration care by management rather than by conventional approaches like coinsurance and deductibles and offer a bundle of characteristics quality access for many services that is fundamentally outside the scope of direct regulation selection related incentives threaten the efficiency and fairness of this organization of health insurance markets by inducing plans to distort the quality of the services they offer to discourage high cost persons from joining the plan as managed care becomes the predominant source of health care for residents of the united states and many other countries payers attempt to address this incentive by setting a risk adjusted price that pays more for more expensive enrollees as it is conventionally practiced risk adjustment sets prices for people proportional to their expected cost based on observable characteristics the federal medicare program for example has used age sex welfare status and county of residence adjusters to set prices to managed care plans to convey how what we term conventional risk adjustment works suppose age is the risk adjuster for a medicare population over 65 if it is determined that the 75to 84 year old population costs 20 percent more than the overall average in medicare the assumption in conventional risk adjustment is that the premium paid to plans for someone in this group should be 20 percent above the average we fundamentally disagree that this is the right way to think about and do risk adjustment

competitive insurance markets under adverse selection and capacity constraints abstract ever since the seminal work by rothschild and stiglitz q j econom 90 1976 629 on competitive insurance markets under adverse selection the problem of non existence of equilibrium in pure strategies has received much attention in the literature we extend the original analysis by considering firms which face capacity constraints which might be due to limited capital we show that under mild assumptions an equilibrium exists where every consumer obtains his appropriate rothschild stiglitz contract

adverse selection and inertia in health insurance markets when nudging hurts this paper investigates consumer inertia in health insurance markets where adverse selection is a potential concern we leverage a major change to insurance provision that occurred at a large firm to identify substantial inertia and develop and estimate a choice model that also quantifies risk preferences and ex ante health risk we use these estimates to study the impact of policies that nudge consumers toward better decisions by reducing inertia when aggregated these improved individual level choices substantially exacerbate adverse selection in our setting leading to an overall reduction in welfare that doubles the existing welfare loss from adverse selection jel d82 g22 i13 a number of potential impediments stand in the way of efficient health insur ance markets the most noted of these is adverse selection first studied by akerlof 1970 and rothschild and stiglitz 1976 in insurance markets prices reflect the expected risk costs of the insured pool whether the reason is price regulation or private information when insurers cannot price all risk characteristics riskier consumers choose more comprehensive health plans this causes the equilibrium prices of these plans to rise and healthier enrollees to select less comprehensive coverage than they would otherwise prefer

estimating risk preferences from deductible choice we develop a structural econometric model to estimate risk preferences from data on deductible choices in auto insurance contracts we account for adverse selection by modeling unobserved heterogeneity in both risk claim rate and risk aversion we find large and skewed heterogeneity in risk attitudes in addition women are more risk averse than men risk aversion exhibits a u shape with respect to age and proxies for income and wealth are positively associated with absolute risk aversion finally unobserved heterogeneity in risk aversion is greater than that of risk and as we illustrate has important implications for insurance pricing

a game theoretic foundation of competitive equilibria with adverse selection we construct an extensive form game that captures competitive markets with adverse selection it allows firms to offer any finite set of contracts so that cross subsidization is not ruled out moreover firms can withdraw from the market after initial contract offers have been observed we show that a subgame perfect equilibrium always exists in fact when withdrawal is costless the set of equilibrium outcomes may correspond to the entire set of feasible contracts we then focus on robust equilibria that continue to exist for small withdrawal costs we show that the miyazaki wilson contracts are the unique robust equilibrium outcome

a walrasian theory of markets with adverse selection the paper describes a walrasian theory of markets with adverse selection and shows how refinements of equilibrium can be used to characterize uniquely the equilibrium outcome equilibrium exists under standard conditions it is shown that under certain conditions a stable set exists and is contained in a connected set of equilibria for generic models there exists a stable outcome that is all the equilibria in the stable set have the same outcome these ideas are applied to markets with one sided and two sided uncertainty under standard monotonicity conditions it is shown that the stable outcome is separating and implies a particular pattern of matches of buyers and sellers

federalism chinese style the political basis for economic success in china china s remarkable economic success rests on a foundation of political reform providing a considerable degree of credible commitment to markets this reform reflects a special type of institutionalized decentralization that the authors call federalism chinese style this form of decentralization has three consequences first it fosters competition not only in product markets but also among local governments for labor and foreign capital this competition in turn encourages local government experimentation and learning with new forms of enterprises regulation and economic relationships second it provides incentives for local governments to promote local economic prosperity finally it provides a significant amount of protection to local governments and their enterprises from political intrusion by the central government

adverse selection and an individual mandate when theory meets practice we develop a model of selection that incorporates a key element of recent health reforms an individual mandate using data from massachusetts we estimate the parameters of the model in the individual market for health insurance we find that premiums and average costs decreased significantly in response to the individual mandate we find an annual welfare gain of 4 1 per person or 51 1 million annually in massachusetts as a result of the reduction in adverse selection we also find smaller post reform markups