nonparametric bounds on the returns to language skills this paper applies the theoretical literature on nonparametric bounds on treatment effects to the estimation of how limited english proficiency lep affects wages and employment opportunities for hispanic workers in the united states i analyse the identifying power of several weak assumptions on treatment response and selection and stress the interactions between lep and education occupation and immigration status i show that the combination of two weak but credible assumptions provides informative upper bounds on the returns to language skills for certain subgroups of the population adding age at arrival as a monotone instrumental variable also provides informative lower bounds copyright 2005 john wiley sons ltd

negotiation and renegotiation of optimal financial contracts under the threat of predation this paper examines the effect of renegotiation on the ability of financial contracts between a lender and entrant to deter an incumbent s predation in the presence of renegotiation it is more difficult for the entrant to obtain financing and more difficult for the contract to deter predation contracts successfully deter predation in some cases however even if renegotiation occurs at a stage with symmetric information between the entrant and lender giving the entrant constrained by limited liability stronger bargaining power vis a vis the lender improves the efficiency of the optimal contract but the results concerning renegotiation are unchanged copyright 1996 by blackwell publishing ltd

financial aid debt management and socioeconomic outcomes post college effects of merit based aid abstract prior research has demonstrated that financial aid can influence both college enrollments and completions but less is known about its post college consequences this study is the first to link college and financial aid information to credit bureau data later in life enabling us to examine the impacts of grant aid on homeownership neighborhood characteristics and credit outcomes we use a regression discontinuity rd strategy to identify causal effects of the wv promise scholarship a broad based state merit aid program up to 10 years after college entry the rd is imperfect because our sample is limited to college students and the scholarship program increased enrollment but there is little evidence of selection on observables at the threshold we find that scholarship recipients near the test score cutoff for eligibility are more likely to earn a graduate degree are more likely to own a home and live in higher income neighborhoods effects on annual earnings and credit outcomes are similarly positive but imprecise these positive effects are primarily due to substantial reductions in time to degree rather than to reduced student debt upon graduation

micro data heterogeneity and the evaluation of public policy nobel lecture this paper summarizes the contributions of microeconometrics to economic knowledge four main themes are developed 1 microeconometricians developed new tools to respond to econometric problems raised by the analysis of the new sources of micro data produced after the second world war 2 microeconometrics improved on aggregate time series methods by building models that linked economic models for individuals to data on individual behavior 3 an important empirical regularity detected by the field is the diversity and heterogeneity of behavior this heterogeneity has profound consequences for economic theory and for econometric practice 4 microeconometrics has contributed substantially to the scientific evaluation of public policy

head start and the distribution of long term education and labor market outcomes we investigate the effect of head start on education and wage income for individuals in their 30s in the nlsy79 we contribute to the existing literature by examining effects across outcome distrib

the estimation of wage gains and welfare gains in self selection models the authors modify the basic self sele ction model for the effects ofeducation training unions and other activities on wages by including heterogeneity of rewards to the activity i e diffe rences across individuals in the rate of return to the activity the authors sho w that such heterogeneity creates a new form of selectionbias they provide tes ts for its presence and draw out its implications for the wage and welfare gains to the activity an empirical application provides strong support for such hete rogeneityin one particular training program copyright 1987 by mit press

identification issues in the public private wage gap with an application to italy this paper reviews some of the standard assumptions that are imposed in order to estimate the average public private wage gap and that are mainly related to the possible selection of the sector there are two contributions to the existing public private wage gap literature one is a better understanding of the identified parameters standard estimators identify a local effect late which in general cannot be generalized to the entire population as instead is almost always done the other is the partial identification of the population average treatment effect with an instrumental variable to the best of my knowledge this is the first paper in this literature that employs bounds the technique is applied to male workers in italy for compliers late estimates a wage advantage from working in the public sector greater than 30 this return is within the narrowest bounds on the population average treatment effect that are consistent even with a much smaller gap about 15 or more

the principal agent relationship with an informed principal ii common values in many circumstances a principal may have relevant private information when she proposes a contract to an agent we analyze such a principal agent relationship as a noncooperative game the principal proposes a contract which is accepted or rejected by the agent who for most of our analysis has no private information the contract is executed if accepted otherwise the reservation allocation takes effect this allocation may be determined by a pre existing contract which the principal by her proposal is attempting to renegotiate or it may simply be the no trade point in this paper we assume that the principal s information directly affects the agent s payoff before solving the game we discuss pareto efficiency with asymmetric information we define an incentive compatible allocation to be weakly interim efficient wie if there exists no alternative incentive compatible allocation that both parties prefer for all possible beliefs that the agent might have about the principal s private information type we show that any wie allocation is interim efficient ie for some beliefs the rothschild stiglitz wilson rsw allocation relative to the reservation allocation l is the allocation that maximizes the payoff of each type of principal within the class of incentive compatible allocations that guarantee the agent at least the utility he gets from a irrespective of his beliefs about the principal s type the equilibrium set of the contract proposal game consists of the allocations that weakly pareto dominate the rsw allocation thus there is a unique equilibrium outcome if and only if the latter is ie and the equilibrium outcome is the rsw allocation itself after characterizing the equilibrium allocations we study those that are renegotiation proof when either the principal or the agent leads the renegotiation we then compare our contract proposal game which is a signaling model with its screening counterpart we conclude by extending our results to the case in which the agent as well as the principal has private information under the assumption of quasi linear preferences

the returns to schooling a selectivity bias approach with a continuous choice variable the essence of selection bias is that we do not observe nonoptimal choices this applies whether the choice variable is discrete or continuous this paper extends the selection bias methodology to the case where the choice variable is continuous and the choice set is ordered the leading practical application of this analysis is the schooling choice problem schooling is treated as a continuous choice variable and selectivity corrected rates of return are estimated the findings suggest selectivity is of considerable importance and support the comparative advantage hypothesis of willis and rosen 18

generating skilled self employment in developing countries experimental evidence from uganda we study a government program in uganda designed to help the poor and unemployed become self employed artisans increase incomes and thus promote social stability young adults in uganda s conflict affected north were invited to form groups and submit grant proposals for vocational training and business start up funding was randomly assigned among screened and eligible groups treatment groups received unsupervised grants of 382 per member grant recipients invest some in skills training but most in tools and materials after four years half practice a skilled trade relative to the control group the program increases business assets by 57 work hours by 17 and earnings by 38 many also formalize their enterprises and hire labor we see no effect however on social cohesion antisocial behavior or protest effects are similar by gender but are qualitatively different for women because they begin poorer meaning the impact is larger relative to their starting point and because women s work and earnings stagnate without the program but take off with it the patterns we observe are consistent with credit constraints

asset stock accumulation and sustainability of competitive advantage given incomplete factor markets appropriate time paths of flow variables must be chosen to build required stocks of assets that is critical resources are accumulated rather than acquired in strategic factor markets barney barney j 1986 strategic factor markets expectations luck and business strategy management sci october 1231 1241 sustainability of a firm s asset position hinges on how easily assets can be substituted or imitated imitability is linked to the characteristics of the asset accumulation process time compression diseconomies asset mass efficiencies inter connectedness asset erosion and causal ambiguity

sharp iv bounds on average treatment effects on the treated and other populations under endogeneity and noncompliance in the presence of an endogenous binary treatment and a valid binary instrument causal effects are point identified only for the subpopulation of compliers given that the treatment is monotone in the instrument with the exception of the entire population causal inference for further subpopulations has been widely ignored in econometrics we invoke treatment monotonicity and or dominance assumptions to derive sharp bounds on the average treatment effects on the treated as well as on other groups furthermore we use our methods to assess the educational impact of a school voucher program in colombia and discuss testable implications of our assumptions

strategic investment and timing of entry the authors introduce competition over entry time into a sequential output choice model to show how profit differences will be dissipated this resolves a problem in the standard stackelberg model that the order of moves is exogenously specified yet an earlier position in the order is usually preferred to a later one if capacity costs are not too low the authors solution applies even if firms cannot commit to sell their entire output introducing positive capacity costs slightly modifies the static stackelberg results since endogenous cost asymmetries arise the framework therefore partially rehabilitates the stackelberg model copyright 1994 by economics department of the university of pennsylvania and the osaka university institute of social and economic research association

monotone instrumental variables with an application to the returns to schooling for fifty years econometric analyses of treatment response have made extensive use of instrumental variable iv assumptions holding that mean response is constant across specified subpopulations of a population of interest 2 yet the credibility of mean independence conditions and other iv assumptions has often been a matter of considerable disagreement with much debate about whether some covariate is or is not a valid instrument in an application of interest there is therefore good reason to consider weaker but more credible assumptions to this end we introduce monotone instlumental variable miv assumptions holding that mean response varies weakly monotonically across specified subpopulations we study the identifying power of these miv assumptions and give an empirical application the findings reported here add to the literature developing nonparametric bounds on treatment effects 3 this paper uses the same formal setup as manski 1997 there is a probability space j x2 p of individuals each member j of population j has observable covariates xi e x and a response function yj t y mapping the mutually exclusive and exhaustive treatments t e t into outcomes yj t e y person j has a realized treatment zj e t and a realized outcome y 1 y zi both of which are observable the latent outcomes yj t

sunk costs entry deterrence and financial constraints this paper studies how sunk costs affect a financially constrained incumbent s ability to deter entry into its market sunk costs make it less attractive to the incumbent to accommodate entry by liquidating assets in place and exiting the market this may render entry by a prospective rival unprofitable and thereby facilitate entry deterrence however sunk costs also make it harder for the incumbent to pledge valuable collateral to outside investors to make up for the poor collateral value the incumbent will have to give stronger liquidation rights to its lenders consequently a larger fraction of the incumbent s assets will be liquidated in the event of a liquidity default this potentially creates room for profitable entry the overall effect of sunk costs on the incumbent s ability to deter entry into its market is thus ambiguous

misreported schooling and returns to education evidence from the uk this paper aims to provide a number of contributions of policy practical and methodological interest to the study of the returns to educational qualifications first we derive estimates of the returns to different qualifications for the uk that allow for the possibility of misreported attainment using data from the british national child development survey to date any major empirical evidence on the importance of this issue is restricted to the us where it was shown that errors might indeed play a non negligible role second we aim to provide the academic and policy community with estimates of the accuracy of commonly used types of data on educational attainment administrative files self reported information close to the date of completion of the qualification and recall information ten years after completion third by using the unique nature of our data we assess how the biases from measurement error and from omitted ability and family background variables interact in the estimation of returns we intend to produce simple calibration rules to allow policymakers to use nationally representative data such as the labour force survey that totally rely on self reported information on qualifications and contain little or no information on individual ability and family background we rely throughout on a unified framework of general applicability to study the impact of misreported treatment status on the estimation of causal treatment effects jel codes c10 i20 j31

food stamps and food insecurity what can be learned in the presence of nonclassical measurement error policymakers have been puzzled to observe that food stamp households appear more likely to be food insecure than observationally similar eligible nonparticipating households we reexamine this issue allowing for nonclassical reporting errors in food stamp participation and food insecurity extending the literature on partially identified parameters we introduce a nonparametric framework that makes transparent what can be known about conditional probabilities when a binary outcome and conditioning variable are both subject to nonclassical measurement error we find that the food insecurity paradox hinges on assumptions about the data that are not supported by the previous food stamp participation literature

partial identification of counterfactual choice probabilities this article shows how to predict counterfactual discrete choice behavior when the presumed behavioral model partially identifies choice probabilities the simple general approach uses observable choice probabilities to partially infer the distribution of types in the population and then applies the results to predict behavior in unrealized choice settings two illustrative applications are given one assumes only that persons have strict preferences the other assumes strict preferences and utility functions that are linear in attribute bundles with no restrictions on the shape of the distribution of preference parameters

evaluating education programs that have lotteried admission and selective attrition we study the effectiveness of magnet programs in an urban district that ration excess demand by admission lotteries differential attrition arises since students who lose the lottery are more likely to pursue options outside the school district than students who win the lottery when students leave the district important outcome variables are often not observed the treatment effects are not point identified we exploit known quantiles of the outcome distribution to construct informative bounds on treatment effects we find that magnet programs improve behavioral outcomes but have no significant effect on achievement

anonymity or distance job search and labour market exclusion in a growing african city we show that helping young job seekers signal their skills to employers generates large and persistent improvements in their labour market outcomes we do this by comparing an intervention that improves the ability to signal skills the job application workshop to a transport subsidy treatment designed to reduce the cost of job search in the short run both interventions have large positive effects on the probability of finding a formal job the workshop also increases the probability of having a stable job with an open ended contract four years later the workshop significantly increases earnings job satisfaction and employment duration but the effects of the transport subsidy have dissipated gains are concentrated on individuals who generally have worse labour market outcomes overall our findings highlight that young people possess valuable skills that are unobservable to employers making these skills observable generates earnings gains that are far greater than the cost of the intervention

information mobile telephony and traders search behavior in niger information and communications technologies have spread rapidly in developing countries we investigate the impact of mobile phones on traders search behavior in niger by constructing a theoretical model of search in which traders engage in sequential search for the optimal sales price using a trader panel dataset spanning 2005 2007 we find empirical support for the model in that the duration of mobile phone coverage is associated with increased search activity this effect evolves dynamically over time and is stronger for larger traders who engage in arbitrage over longer distances results provide empirical evidence for the observed linkages between mobile telephony and price dispersion

set identification in models with multiple equilibria we propose a computationally feasible way of deriving the identified features of models with multiple equilibria in pure or mixed strategies it is shown that in the case of shapley regular normal form games the identified set is characterized by the inclusion of the true data distribution within the core of a choquet capacity which is interpreted as the generalized likelihood of the model in turn this inclusion is characterized by a finite set of inequalities and efficient and easily implementable combinatorial methods are described to check them in all normal form games the identified set is characterized in terms of the value of a submodular or convex optimization program efficient algorithms are then given and compared to check inclusion of a parameter in this identified set the latter are illustrated with family bargaining games and oligopoly entry games copyright 2011 oxford university press

modeling the dynamics of strategic fit a normative approach to strategic change this study develops and tests a dynamic perspective on strategic fit drawing from contingency and resource based arguments in the strategy and organizational theory literatures we propose a distinctive analytical approach to identify environmental and organizational contingencies that should predict changes in a firm s strategy and the performance implications of such changes we test our model using extensive longitudinal data from over 4000 u s savings and loan institutions during a period when many s ls considered changing strategic direction the findings support our model of dynamic strategic fit specifically we find that 1 the timing direction and magnitude of strategic changes can be logically predicted based on differences in specific environmental forces and organizational resources and 2 organizations that deviated from our model s prediction of dynamic strategic fit i e changed more or changed less than our model prescribed experienced negative performance consequences we conclude by discussing the implications of our approach and findings for future research on strategic fit and strategic change copyright 2000 john wiley sons ltd

treatment effect heterogeneity in theory and practice instrumental variables iv methods identify internally valid causal effects for individuals whose treatment status is manipulable by the instrument at hand inference for other populations requires homogeneity assumptions this paper outlines a theoretical framework that nests causal homogeneity assumptions these ideas are illustrated using sibling sex composition to estimate the effect of childbearing on economic and marital outcomes the application is motivated by american welfare reform the empirical results generally support the notion of reduced labour supply and increased poverty as a consequence of childbearing but evidence on the impact of childbearing on marital stability and welfare use is more tenuous

the conditioning effect of time on firm survival an industry life cycle approach in an effort to reconcile theoretical blind spots we integrated research in technology management organizational ecology and evolutionary economics the central premise underlying the resultan

are ols estimates of the return to schooling biased downward another look the authors examine evidence on bias in ols estimates of the economic return to schooling to study omitted ability bias they use test scores available in the national longitudinal survey of youth as proxies for ability allowing for measurement error in these test scores the authors also explore biases from the endogeneity of schooling or experience or measurement error in these variables in their data ols estimation including test scores appears to be appropriate and indicates an upward bias of roughly 40 percent in the ols estimate ignoring ability this contrasts with evidence from other recent research using different statistical experiments to purge schooling of its correlation with the wage equation error copyright 1995 by mit press

a two stage model of research and development with endogenous second mover advantages this paper describes a simple two stage model of research and development in which the winner of the research stage has the option of moving first in the development stage some unexpected results emerge in equilibrium the leader in the development stage invests less than each follower and is consequently least likely to collect the patent moreover the leader receives a lower expected payoff than each of the followers thus there are endogenous second mover advantages using a game of timing in which the identity of the stackelberg leader is determined to link the two stages i find that firms face quite different incentives in the research stage although the leader invests less than each follower in the research stage as well the leader enjoys higher expected revenue from the complete two stage game than does each follower the equilibrium is inefficient because there is a lag between the time at which research is completed and the time at which development is begun and because aggregate investment is inefficiently asymmetrically distributed across firms

the 2009 lawrence r klein lecture diversified treatment under ambiguity this article develops a broad theme about treatment under ambiguity through study of a particular decision criterion the broad theme is that a planner may want to cope with ambiguity by diversification assigning observationally identical persons to different treatments study of the minimax regret mr criterion substantiates the theme the article significantly extends my earlier analysis of one period planning with an individualistic treatment and a linear welfare function i show that mr treatment allocations are fractional in a large class of planning problems with nonlinear welfare functions interacting treatments learning and noncooperative aspects

partial identification methods for evaluating food assistance programs a case study of the causal impact of snap on food insecurity we illustrate how partial identification methods can be used to provide credible inferences on the causal impacts of food assistance programs focusing on the impact that the supplemental nutrition assistance program snap formerly known as the food stamp program has on food insecurity among households with children recent research applies these methods to address two key issues confounding identification missing counterfactuals and nonrandomly misclassified treatment status in this paper we illustrate and extend the recent literature by using data from the survey of income and program participation sipp to study the robustness of prior conclusions the sipp confers important advantages the detailed information about income and eligibility allows us to apply a modified discontinuity design to sharpen inferences and the panel nature allows us to reduce uncertainty about true participation status we find that snap reduces the prevalence of food insecurity in households with children by at least six percentage points

recent two stage sample selection procedures with an application to the gender wage gap recently developed two stage estimation methods of sample selection models are used in the context of data from the 1989 labor market activity survey to examine labor supply decisions and wage outcomes for employed men and women recent hypothesis test procedures are used to test for no sample selection and to test for a parametric against a semiparametric selection correction procedure we conclude that selection is indeed an issue for the sample at hand and that the semiparametric specification is appropriate we also present the standard decomposition of the gender wage gap into its explained and unexplained portions

mobile phone coverage and producer markets evidence from west africa mobile phone coverage has expanded considerably throughout the developing world particularly within sub saharan africa existing evidence suggests that increased access to information technology has improved agricultural market efficiency for consumer markets and certain commodities but there is less evidence of its impact on producer markets building on the work of aker 2010 this paper estimates the impact of mobile phone coverage on producer price dispersion for three commodities in niger the results suggest that mobile phone coverage reduces spatial producer price dispersion by 6 percent for cowpea a semi perishable commodity these effects are strongest for remote markets and during certain periods of the year the introduction of mobile phone coverage has no effect on producer price dispersion for millet and sorghum two staple grains that are less perishable and are commonly stored by farmers there are no impacts of mobile phone coverage on traders gross margins or producer price levels but mobile phone coverage is associated with a reduction in the intra annual price variation for cowpea these results are potentially explained by the fact that farmers engage in greater storage for storable commodities such as millet and sorghum

the effect of sibling sex composition on women s education and earnings this paper documents the impact of siblings on the education of men and women born in the united states between 1920 and 1965 we examine the effect of the number and sex composition of a boy or girl s siblings on that child s educational attainment we find that throughout the century women s educational choices have been systematically affected by the sex composition of her siblings and that men s choices have not women raised only with brothers have received on average significantly more education than women raised with any sisters controlling for household size since sibling sex composition affects women s educational attainment and plausibly may be unrelated to other determinants of earnings it may provide a useful instrument for education in earnings functions for women our results suggest that standard estimates significantly underestimate the return to schooling for women

adult outcomes for children of teenage mothers using data from the british household panel survey this study examines the relationship between several outcomes in early adulthood e g education inactivity earnings and health and being born to a teenage mother besides standard cross sectional multivariate regression estimates we also present evidence from non parametric estimates and from estimates that account for unmeasured family background heterogeneity by comparing siblings born to the same mother who timed their births at different ages regardless of the econometric technique being born to a teenage mother is usually associated with worse outcomes an important channel of transmission of this adverse effect is childhood family structure which plays a more powerful role than childhood family poverty albeit smaller some of the detrimental effects are also found for children of mothers who gave birth in their early 20s

identification and asymptotic approximations three examples of progress in econometric theory in empirical economics the size and quality of datasets and computational power has grown substantially along with the size and complexity of the econometric models and the population parameters of interest with more and better data it is natural to expect to be able to answer more subtle questions about population relationships and to pay more attention to the consequences of misspecification of the model for the empirical conclusions much of the recent work in econometrics has emphasized two themes the first is the fragility of statistical identification the other related theme involves the way economists make large sample approximations to the distributions of estimators and test statistics i will discuss how these issues of identification and alternative asymptotic approximations have been studied in three research areas analysis of linear endogenous regressor models with many and or weak instruments nonparametric models with endogenous regressors and estimation of partially identified parameters these areas offer good examples of the progress that has been made in econometrics

a theory of dynamic oligopoly ii price competition kinked demand curves and edgeworth cycles we provide game theoretic foundations for the classic kinked demand curve equilibrium and edgeworth cycle we analyze a model in which firms take turns choosing prices the model is intended to capture the idea of reactions based on short run commitment in a markov perfect equilibrium mpe a firm s move in any period depends only on the other firm s current price there are multiple mpe s consisting of both kinked demand curve equilibria and edgeworth cycles in any mpe profit is bounded away from the bertrand equilibrium level we show that a kinked demand curve at the monopoly price is the unique symmetric renegotiation proof equilibrium when there is little discounting we then endogenize the timing by allowing firms to move at any time subject to short run commitments we find that firms end up alternating thus vindicating the ad hoc timing assumption of our simpler model we also discuss how the model can be enriched to provide explanations for excess capacity and market sharing keiiwords tacit collusion markov perfect equilibrium kinked demand curve edgeworth cycle excess capacity market sharing endogenous timing

the rand health insurance experiment three decades later we re present and re examine the analysis from the famous rand health insurance experiment from the 1970s on the impact of consumer cost sharing in health insurance on medical spending we begin by summarizing the experiment and its core findings in a manner that would be standard in the current age we then examine potential threats to the validity of a causal interpretation of the experimental treatment effects stemming from different study participation and differential reporting of outcomes across treatment arms finally we re consider the famous rand estimate that the elasticity of medical spending with respect to its out of pocket price is 0 2 emphasizing the challenges associated with summarizing the experimental treatment effects from non linear health insurance contracts using a single price elasticity

returns to schooling implicit discount rates and black white wage differentials a simple econometric model of investment in schooling is developed and estimated the measure of individual discount rates implicit in their educational investment decisions suggests no difference between individuals from different socioeconomic backgrounds differences in individual speeds of educational attainment which do vary with background explain most of the variation in levels of attainment that is attributable to family background

optimal food price stabilization in a small open developing country in poor countries most governments implement policies aiming to stabilize the prices of staple foods which often include storage and trade measures insulating their domestic market from the world market it is of crucial importance to understand the precise motivations and efficiency of those interventions because they can have consequences worldwide this paper addresses those issues by analyzing the case of a small open developing country confronted by shocks to both the crop yield and foreign price in this model government interventions may be justified by the lack of an insurance market for food prices considering this market imperfection the authors design optimal public interventions through trade and storage policies they show that an optimal trade policy largely consists of subsidizing imports and taxing exports which benefits consumers at the expense of producers import subsidies alleviate the non negativity of food storage in other words when stocks are exhausted subsidizing imports prevents domestic price spikes one striking result an optimal storage policy on its own is detrimental to consumers since its stabilizing benefits leak into the world market and it raises the average domestic price by contrast an optimal combination of storage and trade policies results in a powerful stabilizing effect for domestic food prices

commitment through renegotiation proof contracts with third parties the paper analyzes contracts as means of strategic commitment that is commitment against outside parties to the agreement it considers the example of an incumbent firm which enters a contractual relationship with its workers in order to deter entry it assumes away the possibility for the parties to precommit not to make pareto improving renegotiations of the agreement once entry has taken place under symmetric information the contract is thus found to be useless for entry deterrence if the incumbent firm or workers possess some private information excessive post entry production levels can however be sustained ex post since output reductions may not be incentive compatible while information asymmetries are usually welfare decreasing when the goal is optimal risk sharing they can thus be welfare improving for the contracting parties when commitment against outsiders is the goal of the contract the role of the renegotiation process as a constraint on sustainable agreements is stressed in the paper and the general relevance of strategic contractual commitment is discussed

incumbent positioning as a determinant of strategic response to entry existing research has identified different firm characteristics that determine an incumbent s reaction toward market entrants this study widens the perspective from a firm s absolute attributes to its relative positioning within its competitive environment the hypotheses for the empirical analysis are derived from game theoretic models with either vertical or horizontal product differentiation in each of the two theoretical models two incumbents initially choose very different quality and variety levels respectively and move closer to the center when faced by entry of a competitor from the vertical differentiation model we predict a stronger price reduction by high quality firms in our empirical analysis we are using a novel dataset of the high quality restaurant market in germany to test the theoretical findings while the hypotheses with respect to adjustments of prices and varieties are supported we do not find empirical evidence for the predicted quality adjustment

estimates of the economic returns to schooling from a new sample of twins this paper uses a new survey to contrast the wages of genetically identical twins with different schooling levels multiple measurements of schooling levels were also collected to assess the effect of reporting error on the estimated economic returns to schooling the data indicate that omitted ability variables do not bias the estimated return to schooling upward but that measurement error does bias it downward adjustment for measurement error indicates that an additional year of schooling increases wages by 12 to 16 percent a higher estimate of the economic returns to schooling than has been previously found copyright 1994 by american economic association

drought of opportunities contemporaneous and long term impacts of rainfall shocks on human capital higher wages are generally thought to increase human capital production particularly in the developing world we introduce a simple model of human capital production in which investments and time allocation differ by age using data on test scores and schooling from rural india we show that higher wages increase human capital investment in early life in utero to age 2 but decrease human capital from age 5 to 16 children switch out of school into productive work when rainfall is higher the opportunity cost of schooling even for fairly young children is an important factor in determining overall human capital investment

does compulsory school attendance affect schooling and earnings we establish that season of birth is related to educational attainment because of school start age policy and compulsory school attendance laws individuals born in the beginning of the year start school at an older age and can therefore drop out after completing less schooling than individuals born near the end of the year roughly 25 percent of potential dropouts remain in school because of compulsory schooling laws we estimate the impact of compulsory schooling on earnings by using quarter of birth as an instrument for education the instrumental variables estimate of the return to education is close to the ordinary least squares estimate suggesting that there is little bias in conventional estimates every developed country in the world has a compulsory schooling requirement yet little is known about the effect these laws have on educational attainment and earnings 1 this paper exploits an unusual natural experiment to estimate the impact of compulsory schooling laws in the united states the experiment stems from the fact that children born in different months of the year start school at different ages while compulsory schooling laws generally require students to remain in school until their sixteenth or seventeenth birthday in effect the interaction of school entry requirements and compulsory schooling laws compel students born

sacrifice tests for predation in a dynamic pricing model ordover and willig 1981 and cabral and riordan 1997 meet ericson and pakes 1995 abstract to detect the presence of predatory pricing antitrust authorities and courts routinely ask whether a firm sacrifices current profit in exchange for the expectation of higher future profit following the exit of its rival because predatory pricing is an inherently dynamic phenomenon we show in this paper how to construct sacrifice tests for predatory pricing in a modern industry dynamics framework along the lines of ericson and pakes 1995 in particular we adapt the definitions of predation due to ordover and willig 1981 and cabral and riordan 1997 to this setting and construct the corresponding sacrifice tests

procurement and predation dynamic sourcing from financially constrained suppliers abstract this paper studies the relationship between a financially constrained firm and a stronger opponent who is not cash constrained when these firms repeatedly compete in a procurement context we characterize and discuss the procurement agency s optimal strategy when faced with such asymmetric firms we highlight a trade off between the long run benefits from competition and the short run benefits from reduced costs finally we show that to reduce costs in the short run the financially weak firm should be favored in future procurement

sensitivity to exogeneity assumptions in program evaluation in many empirical studies of the effect of social programs researchers assume that conditional on a set of observed covariates assignment to the treatment is exogenous or unconfounded aka selection on observables often this assumption is not realistic and researchers are concerned about the robustness of their results to departures from it one approach e g charles manski 1990 is to entirely drop the exogeneity assumption and investigate what can be learned about treatment effects without it with unbounded outcomes and in the absence of alternative identifying assumptions there are no restrictions on the set of possible values for average treatment effects this does not mean however that all evaluations are equally sensitive to departures from the exogeneity assumption in this paper i explore an alternative approach developed by paul rosenbaum and donald rubin 1983 where the assumption of exogeneity is explicitly relaxed by allowing for a limited amount of correlation between treatment and unobserved components of the outcomes the starting point of the sensitivity analysis is the assumption that the exogeneity assumption is satisfied only conditional on an additional unobserved covariate making assumptions about the effect of the unobserved covariate on the outcome and its correlation with the treatment i trace out the set of possible values for the treatment effect of interest by considering a sufficiently large set of possible correlations with outcomes and treatment one can recover the bounds on the treatment effect derived by manski 1990 the approach here in the spirit of rosenbaum and rubin 1983 and rosenbaum 1995 is to allow only a limited amount of correlation and to judge the sensitivity of average treatment effect estimates to such correlations there are two novel features of the proposed analysis first rather than formulate the sensitivity in terms of coefficients on the unobserved covariate the sensitivity results are presented in terms of partial r values which may be easier to interpret second the partial r values of the unobserved covariates are compared to those for the observed covariates in order to facilitate judgments regarding the plausibility of values necessary to substantially change results obtained under exogeneity the proposed sensitivity analysis is conceptually related to the practice of assessing sensitivity of estimates by comparisons with results obtained by discarding one or more observed covariates james heckman and v joseph hotz 1989 rajeev dehejia and sadek wahba 1999 jeffrey smith and petra todd 2001 the attraction of the sensitivity analysis is that it is more directly relevant one is not interested in what would have happened in the absence of covariates actually observed but in biases that are the result from not observing all relevant covariates

a dynamic game of r and d patent protection and competitive behavior a theory of dynamic optimal resource allocation to r and d in an n firm industry is developed using differential games this technique represents a synthesis of the analytic methods previously applied to the problem static game theory and optimal control the use of particular functional forms allows the computation and detailed discussion of the nash equilibrium in investment rules this paper addresses the problem of resource allocation to research and development among the important issues that a firm engaging in r and d must evaluate are uncertainty regarding the feasibility and profitability of a particular innovation the possibility of a protracted development period the possibility that a rival firm may innovate first capturing either a patent or a significant share of the new market the possibility that a rival firm may imitate the innovation and appropriate some of the profits in the new market in what follows we will develop a theory of optimal resource allocation to research and development which incorporates the aspects of r and d enumerated above we will use a dynamic game theoretic analysis determining the nash equilibrium strategies for n identical firms the availability of perfect patent protection is shown to accelerate development of the innovation and the effect of increasing rivalry is addressed the impact of increasing rivalry on nash equilibrium investment in r and d depends upon the degree of appropriability of rewards if patent protection is perfect then increasing the number of nash rivals results in increased r and d effort however when imitation is rewarded the opposite may be true finally some notions of competitive and perfectly competitive equilibrium are examined in the context of the model developed below

research needs and challenges in the few system coupling economic models with agronomic hydrologic and bioenergy models for sustainable food energy and water systems on october 12 13 a workshop funded by the national science foundation was held at iowa state university in ames iowa with a goal of identifying research needs related to coupled economic and biophysical models within the few system approximately 80 people attended the workshop with about half representing the social sciences primarily economics and the rest from the physical and natural sciences the focus and attendees were chosen so that findings would be particularly relevant to sbe research needs while taking into account the critical connectivity needed between social sciences and other disciplines we have identified several major gaps in existing scientific knowledge that present substantial impediments to understanding the few system we especially recommend research in these areas as a priority for future funding 1 economic models of decision making in coupled systems deliberate human activity has been the dominant factor driving environmental and land use changes for hundreds of years while economists have made great strides in modeling and understanding these choices the coupled systems modeling literature with some important exceptions has not reflected these contributions several paths forward seem fruitful first baseline economic models that assume rationality can be used much more widely than they are currently moreover the current generation of iams that include rational agents have emphasized partial equilibrium studies appropriate for smaller systems to allow this approach to be used to study larger systems the potential for and consequences of general equilibrium effects should be studied as well second it is important to address shortcomings in these models of economic decision making valuable improvements could be gained from developing coupled models that draw insights from behavioral economics many decision makers deviate systematically from actions that would be predicted by strict rationality but very few iams incorporate this behavior potentially leading to inaccurate predictions about the effects of policies and regulations improved models of human adaptation and induced technological change can also be incorporated into coupled models particularly for medium to long run models decisions about adaptation and technological change will have substantial effects on the conclusions and policy implications but more compelling methods for incorporating these changes into modeling are sorely needed in addition some economic decisions are intrinsically dynamic yet few coupled models explicitly incorporate dynamic models economic models that address uncertainty in decision making are also underutilized in coupled models of the few system 2 coupling models across disciplines despite much recent progress established models for one component of the few system often cannot currently produce outcomes that can be used as inputs for models of other components this misalignment makes integrated modeling difficult and is especially apparent in linking models of natural phenomena with models of economic decision making economic agents typically act to maximize a form of utility or welfare that is not directly linked to physical processes and they typically require probabilistic forecasts as an input to their decision making that many models in the natural sciences cannot directly produce we believe that an especially promising approach is the development of bridge models that convert outputs from one model into inputs for another such models can be viewed as application specific reduced form distillations of a richer and more realistic underlying model ideally these bridge models would be developed in collaborative research projects involving economists statisticians and disciplinary specialists and would contribute to improved understanding in the scientific discipline as well 3 model validation and comparison there is little clarity on how models should be evaluated and compared to each other both within individual disciplines and as components of larger iams this challenge makes larger integrated modeling exercises extremely difficult some potential ways to advance are by developing statistical criteria that measure model performance along the dimensions suitable for inclusion in an iam as well as infrastructure and procedures to facilitate model comparisons focusing on the models out of sample distributional forecasting performance as well as that of the iam overall is especially promising and of particular importance moreover applications of iams tend to estimate the effect of hypothetical future policy actions but there have been very few studies that have used these models to estimate the effect of past policy actions these exercises should be encouraged they offer a well understood test bed for the iams and also contribute to fundamental scientific knowledge through better understanding of the episode in question the retrospective nature of this form of analysis also presents the opportunity to combine reduced form estimation strategies with the iams as an additional method of validation

intertemporal price competition alternating price competition between firms selling differentiated products to nonhomogeneous consumers can yield two different types of equilibria one which we call disciplined arises when products are close substitutes another which we call spontaneous emerges when products are more differentiated in disciplined equilibria an implicit threat to cut price further in response to an initial price cut supports quite collusive outcomes which become less collusive as product differentiation increases in spontaneous equilibria no such threat is needed consumers in the smaller market tend to pay a higher price as do consumers served by the more efficient firm copyright 1990 by the econometric society

the commitment value of contracts under dynamic renegotiation we examine why different renegotiation processes can lead to opposite results regarding the commitment value of third party contracts in the presence of asymmetric information our main result is that a contract loses all strategic value if renegotiation is allowed during the production stage rather than only before production begins this result casts serious doubt on the relevance of previous findings which emphasize how contracts can have commitment value even in the presence of renegotiation our analysis can also be used to understand the differences between many of the results in the renegotiation literature

exclusionary contracts and competition for large buyers abstract this paper reconsiders the analysis of the competitive effects of buyer contracts in contrast to the previous literature we do not impose ex ante asymmetry on the contracting opportunities of firms rather we consider a market composed of two segments involving small anonymous and large non anonymous buyers while the large buyers can contract with each other and any firm in the market it is assumed that no such opportunities exist for the small buyers that is neither the large buyers nor firms can make contractual commitments with small buyers firms must supply these buyers based on arms length single price oligopolistic competition in this environment we demonstrate that large buyers will have an incentive to form a coalition with a single firm so as to extract rents from the small customer segment market dominance results the outcome is socially suboptimal as either production takes place at a higher cost than is otherwise possible or there is a monopoly for small buyers with an associated allocative loss

the intergenerational transmission of welfare receipt a nonparametric bounds analysis using a nonparametric bounding method and data from the panel study of income dynamics i examine the effect that growing up in a household that receives aid to families with dependent children af

treatment effects with unobserved heterogeneity a set identification approach we propose the sharp identifiable bounds of the potential outcome distributions using panel data we allow for the possibility that statistical randomization of treatment assignments is not achieved until unobserved heterogeneity is properly controlled for we use certain stationarity assumptions to obtain the sharp bounds our approach allows for dynamic treatment decisions where the current treatment decisions may depend on the past treatments or the past observed outcomes as an empirical illustration we study the effect of smoking during pregnancy on infant birthweight we find that for the group of switchers the infant birthweight of a smoking mother is first order stochastically dominated by that of a nonsmoking mother

better late than nothing some comments on deaton 2009 and heckman and urzua 2009 two recent papers deaton 2009 and heckman and urzua 2009 argue against what they see as an excessive and inappropriate use of experimental and quasi experimental methods in empirical work in economics in the last decade they specifically question the increased use of instrumental variables and natural experiments in labor economics and of randomized experiments in development economics in these comments i will make the case that this move towards shoring up the internal validity of estimates and towards clarifying the description of the population these estimates are relevant for has been important and beneficial in increasing the credibility of empirical work in economics i also address some other concerns raised by the deaton and heckman urzua papers

financially constrained entry in a game with incomplete information in an earlier paper we presented an entry game with a monopolist and a potential entrant facing financial constraints in which the unique perfect equilibrium involved no entry here we consider a one sided incomplete information variant of the game in which the monopolist allows for the possibility that the entrant is committed to endure a price war to the limit of his capability we find a unique sequentially perfect equilibrium in which entry sometimes occurs when it does predatory price wars may result with the incumbent sometimes driving out the entrant but other times eventually abandoning the fight

defending against rival innovation we analyze how an incumbent defends its competitive advantage with a focus on the under examined methods of actively defending against the threats posed by rival innovation we describe delineate and analyze the set of such defenses and their likely effects the set of such defenses differs substantially from many standard defenses such as those aimed at defeating the threat of imitation the further study of these pre emptive innovation defenses is important because these defenses are different and because they can substantially affect the sustainability of firm profits and the pace of different of types of innovation

second mover advantages in the strategic adoption of new technology under uncertainty abstract this paper introduces technological uncertainty into a timing game of new technology adoption it is shown that the timing neither necessarily involves first mover advantages in precommitment equilibria reinganum review of economic studies xlviii 1981 395 405 nor rent equalization due to the threat of preemption fudenberg and tirole review of economic studies lii 1985 383 401 rather there may be second mover advantages because of informational spillovers furthermore the model predicts that the equilibrium payoffs will typically be discontinuous and non monotonic in the probability that the new technology is profitable a welfare analysis reveals several market failures and suggests that policy intervention should adequately depend on the nature of uncertainty and the rate of technological progress

housing mobility programs and economic self sufficiency evidence from a randomized experiment this paper examines the effects of a randomized housing voucher program on individual economic outcomes public housing residents who are offered relocation counseling together with housing vouchers that can only be redeemed in low poverty areas experience a reduction in welfare receipt of between 11 and 16 compared to controls these effects are not accompanied by changes in earnings or employment rates as measured by unemployment insurance records offering families unrestricted housing vouchers without additional counseling appears to have little effect on economic outcomes

bounding causal effects using data from a contaminated natural experiment analysing the effects of teenage childbearing in this paper we consider what can be learned about causal effects when one uses a contaminated instrumental variable in particular we consider what inferences can be made about the causal effect of teenage childbearing on a teen mother s subsequent outcomes when we use the natural experiment of miscarriages to form an instrumental variable for teen births miscarriages might not meet all of the conditions required for an instrumental variable to identify such causal effects for all of the observations in our sample however it is an appropriate instrumental variable for some women namely those pregnant women who experience a random miscarriage although information from typical data sources does not allow one to identify these women we show that one can adapt results from horowitz and manski 1995 on identification with data from contaminated samples to construct informative bounds on the causal effect of teenage childbearing we use these bounds to re examine the effects of early chilbearing on the teen mother s subsequent educational and labour market attainment as considered in hotz mcelroy and sanders 1995a 1995b consistent with their study these bounds indicate that women who have births as teens have higher labour market earnings and hours worked compared to what they would have attained if their childbearing had been delayed

market structure and multiple equilibria in airline markets we provide a practical method to estimate the payoff functions of players in complete information static discrete games with respect to the empirical literature on entry games originated by bresnahan and reiss 1990 and berry 1992 the main novelty of our framework is to allow for general forms of heterogeneity across players without making equilibrium selection assumptions we allow the effects that the entry of each individual airline has on the profits of its competitors its competitive effects to differ across airlines the identified features of the model are sets of parameters partial identification such that the choice probabilities predicted by the econometric model are consistent with the empirical choice probabilities estimated from the data we apply this methodology to investigate the empirical importance of firm heterogeneity as a determinant of market structure in the u s airline industry we find evidence of heterogeneity across airlines in their profit functions the competitive effects of large airlines american delta united are different from those of low cost carriers and southwest also the competitive effect of an airline is increasing in its airport presence which is an important measure of observable heterogeneity in the airline industry then we develop a policy experiment to estimate the effect of repealing the wright amendment on competition in markets out of the dallas airports we find that repealing thewright amendment would increase the number of markets served out of dallas love

estimating the effect of financial aid offers on college enrollment a regression discontinuity approach an important problem faced by colleges and universities that of evaluating the effect of their financial aid offers on student enrollment decisions is complicated by the likely endogeneity of the aid offer variable in a student enrollment equation this article shows how discontinuities in an east coast college s aid assignment rule can be exploited to obtain credible estimates of the aid effect without having to rely on arbitrary exclusion restrictions and functional form assumptions semiparametric estimates based on a regression discontinuity rd approach affirm the importance of financial aid as an effective instrument in competing with other colleges for students

education and earnings in the netherlands an empirical analysis abstract in this paper three models which describe the relation between earnings and education are estimated using one single data set one model is a simple dummy regression model in which the educational variables are exogenous both other models take account of the fact that individuals choose their optimal amount of education and is therefore endogenous in all three models i try to specify the equations in the same way as others have done with other data sets it turns out that in each model important conclusions reached in earlier research are not supported by the empirical findings reported here

nonparametric continuous discrete choice models modeling choices that are both discrete and continuous is important in several settings the purpose of this article is to explore formulation and identification of such models when indirect utility functions are specified nonparametrically here we consider general nonseparable disturbances we give identification results for nonseparable sample selection models and use these to analyze identification of discrete continuous choice models

nonparametric bounds on treatment effects assume that each member of a population is characterized by values for the variables ya yb z x here x is a vector describing a person and z is a binary variable indicating which of two treatments this person receives the treatments are labelled a and b the variables ya and yb are scalar measures of the outcomes of the two treatments for example a cancer patient might be treated by a drug therapy or b surgery the relevant outcome y might be life span following treatment an unemployed worker might be given a vocational training or b job search assistance here the relevant outcome might be labor force status following treatment assume that a random sample is drawn and that one observes the realizations of z x and of the outcome under the treatment received thus ya is observed if treatment a is received but is a latent variable if treatment b is received similarly yb is either observed or latent suppose that one wants to learn the difference in expected outcome if all persons with attributes x were assigned to treatment a or b this treatment effect is

omitted ability bias and the increase in the return to schooling over the 1980s there were sharp increases in the return to schooling estimated with conventional wage regressions we explore whether the relationship between ability and schooling changed over this period in ways that would have increased the schooling coefficient in these regressions our empirical results reject the hypothesis that an increase in the bias of the schooling coefficient due to a change in the relationship between ability and schooling has contributed to observed increases in the return to schooling we also find that the increase in the schooling return has occurred for workers with relatively high levels of academic ability

substitution and dropout bias in social experiments a study of an influential social experiment this paper considers the interpretation of evidence from social experiments when persons randomized out of a program being evaluated have good substitutes for it and when persons randomized into a program drop out to pursue better alternatives using data from an experimental evaluation of a classroom training program we document the empirical importance of control group substitution and treatment group dropping out evidence that one program is ineffective relative to close substitutes is not evidence that the type of service provided by all of the programs is ineffective although that is the way experimental evidence is often interpreted

what do instrumental variable models deliver with discrete dependent variables we study models with discrete endogenous variables and compare the use of two stage least squares 2sls in a linear probability model with bounds analysis using a nonparametric instrumental variable model 2sls has the advantage of providing an easy to compute point estimator of a slope coefficient which can be interpreted as a local average treatment effect late however the 2sls estimator does not measure the value of other useful treatment effect parameters without invoking untenable restrictions the nonparametric instrumental variable iv model has the advantage of being weakly restrictive so more generally applicable but it usually delivers set identification nonetheless it can be used to consistently estimate bounds on many parameters of interest including for example average treatment effects we illustrate using data from angrist evans 1998 and study the effect of family size on female employment

monopsony power in migrant labor markets evidence from the united arab emirates by exploiting a reform in the united arab emirates that relaxed restrictions on employer transitions we provide new estimates of the monopsony power of firms over migrant workers our results show that the reform increased incumbent migrants earnings and firm retention this occurs despite an increase in employer transitions and is driven by a fall in country exits while the outcomes of incumbents improved the reform decreased demand for new migrants and lowered their earnings these results are consistent with a model of monopsony in which firms face upward sloping labor supply curves for both new recruits in source countries and incumbent migrants