computing multi period information constrained optima this paper presents a detailed theoretical derivation and justification for methods used to compute solutions to a multi period including infinite period continuum agent unobservedeffort economy actual solutions are displayed illustrating cross sectional variability in consumption and labour effort in the population at a point in time and variability for a typical individual over time the optimal tradeoff between insurance and incentives is explored and the issue of excess variability is addressed by consideration of the analogue full information economy and various restricted contracting regimes

the informational content of implied volatility implied volatility is widely believed to be informationally superior to historical volatility because it is the markets forecast of future volatility but for s p 100 index options the most actively traded contract in the united states we find implied volatility in aggregate and across subsamples separated by maturity and strike price implied volatility has virtually no correlation with future volatility and it does not incorporate the information contained in recent observed volatility article published by oxford university press on behalf of the society for financial studies in its journal the review of financial studies

multivariate tests of the zero beta capm abstract a cross sectional regression test csrt of the capm is developed and its connection to the hotelling t2 test of multivariate statistical analysis is explored algebraic relations between the csrt the likehood ratio test and the langrange multiplier test are derived and a useful small sample bound on the distribution function of the csrt is obtained an application of the csrt suggests that the crsp equally weighted index is inefficient but that the inefficiency is not explained by a firm size effect from february to december

job displacement relative wage changes and duration of unemployment using special cps data on displaced workers this article investigates the wage consequences of job displacement in a framework that emphasizes the effects of past job duration s and unemployment duration s on postdisplacement wages our model also attempts to take account of the simultaneity between unemployment duration and the postdisplacement wage it is found that duration strongly reduces subsequent earnings and that considerable overstatement of the loss in firm specific training investments is implied by conventional routes to measuring wage losses

tick size share prices and stock splits minimum price variation rules help explain why stock prices vary substantially across countries and other curiosities of share prices companies tend to split their stock so that the institutionally mandated minimum tick size is optimal relative to the stock price a large relative tick size provides an incentive for dealers to make markets and for investors to provide liquidity by placing limit orders despite its placing a high floor on the quoted bid ask spread a simple model suggests that idiosyncratic risk firm size and visibility of the firm affect the optimal relative tick size and thus the share price in stock markets around the world the average price per share differs substantially the median u s stock for example sells for about 40 a typical london stock sells for about 5 7 50 and a typical hong kong share is about 2 furthermore when stock prices rise above a country s usual trading range firms often split their stocks to restore prices to that range why are these price ranges so different among countries these trading ranges can be remarkably stable over time during the half century from 1943 to 1994 the s p composite index increased over 1 500 percent yet the average new york stock exchange nyse share price was

the economic consequences of labor mobility unlike most previous research on the relative changes in earnings of job stayers and job changers this study examines the variance in earnings changes rather than simply average changes men and women rather than only men and the five year period following job change rather than only the first year or two the author finds great variability in earnings changes both within and across race and gender groups notably men gained more from quits and except in the case of low wage workers lost less from layoffs than women also men suffered a much smaller penalty than women for repeated job changes for all groups the percentage difference between earnings before and after leaving a job generally persisted for several years

measurement effects and the variance of returns after stock splits and stock dividends this article examines the relation between two factors affecting stock returns the bid ask spread and price discreteness and the increase in return variance after ex dates of stock splits and stock dividends controlling for these effects the variance of daily returns still increases significantly the variance of weekly returns also increases significantly and the variance of returns for a control sample of nonsplitting firms shows no significant increase variance ratio tests show that bid ask errors are small for these stocks and therefore cannot explain the large increase in variance spreads and price discreteness do not explain increased variance after stock distributions article published by oxford university press on behalf of the society for financial studies in its journal the review of financial studies

unemployment duration stigma and re employment earnings a nonstationary model of individual labor market histories where the distribution of wages offers depends on elapsed unemployment duration and where unemployment compensation is claimed for a limited period only is estimated from sample information on completed unemployment duration accepted earnings and accepted job duration and can identify movements in the reservation wages induced by human capital loss from those caused by benefit exhaustion the results indicate that individuals seem to be much more sensitive to benefit exhaustion than human capital loss the estimated structural parameters provide an explanation for the existence of a statistical relationship between continuous unemployment and accepted job durations

short term contracts and long term agency relationships abstract long term contracts are valuable only if optimal contracting requires commitment to a plan today that would not otherwise be adopted tomorrow we show that commitments are unnecessary and hence short term contracts are sufficient if 1 all public information can be used in contracting 2 the agent can acess a bank on equal terms with the principal 3 recontracting takes place with common knowledge about technology and preferences and 4 the frontier of expected utility payoffs generated by the set of incentive compatible contracts is downward sloping at all times

efficiency and equality in a simple model of efficient unemployment insurance abstract this paper describes the efficient allocation of consumption and work effort in an economy in which workers face idiosyncratic employment risk and considerations of moral hazard prevent full insurance we impose a lower bound on the expected discounted utility that can be assigned to any agent from any date onward and show with this feature added that the efficient unemployment insurance scheme induces an invariant cross sectional distribution of individual entitlements to utility the paper thus provides a simple prototype model suited to the study of the normative question what is the trade off between equality and efficiency in resource allocation journal of economic literature classification numbers d31 d63 d82 j65

optimal unemployment insurance with human capital depreciation and duration dependence this paper studies the effect of human capital depreciation and duration dependence on the design of an optimal unemployment insurance ui scheme our results partially confirm those obtained in most previous studies benefits should decrease with unemployment duration the optimal program also generates two main novel features which are not present in stationary models first if human capital depreciates rapidly enough during unemployment ui transfers are bounded below by a minimal assistance level that arises endogenously in the efficient program second we study the optimality of imposing a history contingent wage tax after reemployment our numerical simulations based on the spanish and us economies show that the wage tax should decrease with the length of worker s previous unemployment spell and become a wage subsidy for long term unemployed workers as a by product of our study we develop a systematic approach suitable for studying recursively a wide range of dynamic moral hazard problems and other models with similar characteristics

the idiosyncratic volatility puzzle time trend or speculative episodes campbell lettau malkiel and xu 2001 document a positive trend in idiosyncratic volatility during the 1962 1997 period we show that by 2003 volatility falls back to pre 1990s levels furthermore we show that the increase and subsequent reversal is concentrated among firms with low stock prices and high retail ownership this evidence suggests that the increase in idiosyncratic volatility through the 1990s was not a time trend but rather an episodic phenomenon at least partially associated with retail investors results from cross sectional regressions conditional trend estimation stock split events and attention grabbing events are consistent with a retail trading effect the author 2009 published by oxford university press on behalf of the society for financial studies all rights reserved for permissions please email journals permissions oxfordjournals org oxford university press

identifying the hand of past distinguishing state dependence from heterogeneity a basic problem in social science is to ascertain the importance of initial endowments on subsequent outcomes of a dynamic process interest in this topic centers on two distinct issues a do initial endowments have a temporally persistent effect on outcomes i e is there heterogeneity b are the effects of initial endowments attenuated or accentuated by subsequent experiences of the process being studied or by related processes i e is there state dependence these two questions show up in a variety of contexts 1 the importance of family background on a person s subsequent education and earnings is a hotly debated topic do market or nonmarket mechanisms reinforce or diminish initial endowments 2 the incidence of criminal activity is concentrated among a small population of repeated offenders are certain persons prone to criminality or does crime breed crime 3 are persons who experience unemployment more likely to experience future unemployment due to loss of work experience or market stigma 4 does early entry into an industry confer an advantage of incumbency or does it merely proxy the basic managerial and innovative ability of early entrants many formal models of state dependent processes or processes with persistent effects of initial conditions have been formulated invariance of steady states to initial endowments was viewed as a desirable feature of an economic model in the 1960 s and 1970 s path dependent synergism and nonergodicity are fashionable features of models today is the choice between models with long run dependence on initial conditions and those without solely a matter of intellectual esthetics can data discriminate between these two classes of models how many economically extraneous statistical regularity conditions have to be imposed in order to distinguish between these models how many and what kind of maintained assumptions are required in order to let the data speak on these important questions in this paper i focus on one nonergodic model that receives much attention in the literature the model of duration dependence and heterogeneity discussed by herbert silcock 1954 and also examined by tony lancaster 1979 chris elbers and geert ridder 1982 myself and burton singer 1984 and myself and bo honore 1989

the role of unemployment insurance in an economy with liquidity constraints and moral hazard the potential welfare benefits of unemployment insurance along with the optimal replacement ratio are studied using a quantitative dynamic general equilibrium model to provide a role for unemployment insurance agents in our economy face exogenous idiosyncratic employment shocks and are unable to borrow or insure themselves through private markets in the absence of moral hazard replacement ratios as high as 65 are optimal and the welfare benefits of unemployment insurance are quite large however if there is moral hazard and the replacement ratio is not set optimally but is instead set to an empirically plausible value the economy can be much worse off than it would be without unemployment insurance

dynamic labour force participation of married women and endogenous work experience this paper presents and estimates a dynamic model of married women s labour force participation and fertility in which the effect of work experience on wages is explicitly taken into account because current participation alters future potential earnings the investment return to work will be an important factor in the current work decision in any forward looking behavioural model the model is estimated using the national longitudinal surveys mature women s cohort we use the estimates of our model to predict changes in the lifecycle patterns of employment due to changes in schooling fertility husband s income and the magnitude of the experience effect on wages we find that although work experience increases the disutility of further work the effect is overwhelmed by the positive effect of experience on wages leading to persistence in the employment patterns of these women in addition we find that an increase in young children and in husband s income substantially reduces participation while increased schooling has a powerful positive impact on participation this paper presents an estimable structural dynamic model of married women s labour force participation and fertility in which wages are stochastic and work experience or cumulative participation is endogeneous the model is structural in the sense that the parameters which are estimated are contained in the fundamental relationships governing behaviour namely the utility function and the constraints the model is contained in the class of models which describe the life cycle capital accumulation process with endogeneous labour supply such as weiss 1972 and heckman 1976 it is closest in spirit to that of weiss and gronau 1981 1 the basic feature of their model and ours is that labour market participation affects future wages which then affects future participation the investment return to current work will necessarily be taken into account in any forward looking optimizing model as weiss and gronau note estimates of labour supply models have ignored the inherent behavioural dynamics associated with a positive wageexperience profile there is no adequate empirical treatment of the human capital investment dimension of the labour force participation decision in the literature heckman and willis 1977 have studied a sequential discrete choice model of the labour force participation of married women in a reduced form framework their work

job contact networks abstract many workers hear about or obtain their jobs through friends and relatives the aim of this paper is twofold first we relate both individual and aggregate labor market outcomes to the network structure of personal contacts second we study strategic network formation to this purpose we develop a model specifying at the individual level both the decision to form contacts with other agents and the process by which information about jobs is obtained and transmitted we show that equilibrium networks always exist and that only moderate levels of network asymmetry can be sustained at equilibrium also we establish a general non monotonicity result on information flow and unemployment with respect to network size in symmetric networks

optimal unemployment insurance this paper considers the design of an optimal unemployment insurance system the problem is modeled as a repeated principalagent problem involving a risk averse agent the unemployed worker and a risk neutral principal which cannot monitor the agent s search effort the optimal long term contract subject to the associated incentive constraints is characterized this contract involves a replacement ratio that decreases throughout the unemployment spell and a wage tax after reemployment that under some mild regularity conditions increases with the lenght of the unemployment spell some numerical results are presented that suggest that the gains from switching to this optimal unemployment insurance scheme could be quite large the performance of this optimal contract is also compared to alternative liquidity provision mechanisms

volatility increases subsequent to nyse and amex stock splits the post split increase in daily returns volatility is less for amex stocks than for nyse stocks the exchange trading location is a significant factor in explaining the volatility shift even after stock price and firm size are considered furthermore when measured on a weekly basis there is no increase in amex stocks returns volatility these results suggest that measurement errors created by bid ask spreads and the 1 8 effect and also one or more of the elements that make the nyse different from the amex explain why the estimated volatility of daily stock returns increases after the ex split date ohlson and penman 1985 provide evidence that nyse stock returns variances increase subsequent to ex stock distribution days for splits of 100 or greater the increase in volatility is independent of the size of the split alnd the post split price seven potential problems that might affect their results are analyzed and rejected 1 ohlson and penman 1985 suggest that the greater post split volatility may be due to the activity of relatively ignorant noisy traders who prefer trading low priced stocks this clientele factor is attributed to black 1986 pg 534 and institutional factors a rather broad category that incorporates measurement problems created by the 1 8 effect and bid ask spreads as possible hypotheses for the post split volatility increase this paper extends ohlson and penman s 1985 analysis to amex stocks exchange listing can serve as a proxy for several real factors that may cause the increase in post split variance many of which are related to the clientele factor and institutional factors cited above if the increase in volatility differs between nyse and amex stocks it will suggest that one or more of the following contributes to the phenomenon

on efficient distribution with private information this paper is a study of the dynamics of the efficient distribution of consumption in an exchange economy with many consumers each of whom is subject to private idiosyncratic taste shocks we propose a recursive method for finding feasible allocations that are incentivecompatible and that are pareto optimal within this set the method is applied to several parametric examples we find that in an efficient allocation the degree of inequality continually increases with a diminishing fraction of the population receiving an increasing fraction of the resources we discuss the extent to which these allocations can be decentralized via market arrangements this paper is a study of the dynamics of the efficient distribution of consumption in an exchange economy with private information the economy we study has a constant endowment flow of a single non storable consumption good which is to be allocated each period among a large number of consumers each period these consumers experience unpredictable idiosyncratic privately observed taste shocks affecting their marginal utility of current consumption efficiency dictates that more resources be allocated to those consumers who in any given period have a high marginal utility of current consumption

optimal unemployment insurance a survey unemployment insurance improves the allocation of risk bearing at the cost of reduced incentives for work in the past two decades a branch of the literature has emerged that deals with the optimal design of unemployment insurance this literature has been influenced by ideas and methods from information economics and by theories from labor economics the result is a collection of models designed to highlight a variety of issues pertaining to the provision of optimal unemployment insurance this paper reviews these issues summarizes the relevant literature assesses its accomplishments and points out problems that require further study

a note on the behavior of stock returns around ex dates of stock distributions stock returns after the ex split date is significantly higher than the presplit volatility the increase in the standard deviation of daily returns is of the order of twenty eight to thirty five percent and persists for as long as a full year after the ex date even more interesting is their finding that there is no permanent change in the variance of returns at the announcement date they investigate several potential explanations for this aberration but are unable to find a satisfactory answer grinblatt masulis and titman 6 henceforth gmt examine the behavior of expected returns around announcement dates and exdates for stock distributions exceeding ten percent classifying stock distributions as either stock dividends split factors of twenty five percent or less or stock splits they conclude that return behavior differs across these two types of distributions with stock dividends exhibiting larger abnormal returns than splits this is interpreted by them as evidence in favor of the retained earnings hypothesis the dissimilar accounting treatment of these two types of stock distributions affects retained earnings in different ways and hence splits are not simply large stock dividends this paper extends the work of op to all types of stock distributions in section i postsplit variance is shown to be different from the presplit variance for small stock splits and stock dividends while small splits display an increase in volatility like large splits stock dividends are associated with a decrease in the volatility of returns this evidence also supports gmt s conclusions that stock splits and stock dividends are different types of events section ii investigates the volatility of returns for reverse splits and demonstrates that postsplit volatility decreases for these events this evidence is complementary to woolridge and chambers 9 findings that reverse splits are also associated with negative abnormal returns at their announcement and ex dates section iii concludes the paper

repeated moral hazard and one sided commitment abstract this paper considers a repeated unobserved endowment economy with a restriction that agents can walk away from insurance contracts at the beginning of any period and contract with another insurer one sided commitment an equilibrium is derived characterized by a unique market determined insurance contract with the property that agents never want to walk away from it the paper shows that trade or insurance still occurs and that a non degenerate long run distribution of consumption exists a numerical example shows that this distribution is nearly log normal journal of economic literature classification numbers d30 d31 d80 d82

beta changes around stock splits revisited recent papers by lamoureux and poon 1987 and brennan and copeland 1988 document a significant permanent increase in average beta subsequent to stock split ex dates this paper demonstrates that the shift in estimated beta following ex dates decays as the measurement interval is lengthened there is no statistically significant difference between pre and post split betas using the scholes williams 1977 estimator and weekly return data or using monthly returns we conclude that lamoureux and poon s and brennan and copeland s results can be attributed to a bias created by using too short a return measurement interval to estimate beta

revisiting the modernization hypothesis longevity and democracy summary modernization theory claims that changes in economic fundamentals like e g income per capita and education levels affect the political structure of a country in a causal way as an important marker of development life expectancy can also be conjectured to have a direct effect on political structures in this paper we estimate the impact of improvements in life expectancy on democracy for the purpose of identification we use data from the international epidemiological transition to construct an instrument for life expectancy we find a statistically and economically significant positive causal effect of improvements in life expectancy on democracy

do earnings increase with job seniority cross sectional wage regressions overstate the extent to which earnings increase with job seniority because they fail to take account of the sorting which occurs when high wage workers have lower rates of mobility the main source of bias is a negative correlation between turnover probabilities and unobserved market valued individual characteristics which are transferable across firms these results argue for the importance of theories which emphasize generally applicable individual differences and against those which focus on firm specific attributes

the effects of stock splits on bid ask spreads this paper examines the effects of stock splits on bid ask spreads for nyse listed companies percentage spreads increase after splits representing a liquidity cost to investors these spread increases are directly related to decreases in share prices following splits and can explain part but not all of the observed increase in return variability after splits the evidence thus suggests a liquidity cost of stock splits that must be weighed against any other perceived benefits of splits such a liquidity cost may validate that stock splits are a signal of favorable information about the firm stock splits have long been a prominent feature in u s financial markets five to ten percent of all amex and nyse firms split in a typical year lakonishok and lev 1987 two potentially conflicting explanations for splits are frequently given first most managers believe baker and gallagher 1980 that splits return share prices to some optimal trading range and improve shareholder liquidity the second explanation is that splits are a costly signal of favorable future prospects for the firm for instance brennan and copeland 1988a show that if stock splits increase liquidity costs to investors such splits can serve as valid signals most empirical studies of the liquidity effects of splits use trading volume copeland 1979 lamoureux and poon 1987 and murray 1985 all conclude that shareholder liquidity decreases after a split based on finding dollar trading volume decreases after splits on the other hand lakonishok and lev 1987 find abnormally high volume in the year preceding a split and abstracting from this abnormal volume that splits are not associated with a change in trading volume the use of volume to measure liquidity is largely motivated by empirical findings of a negative relationship between volume and the bid ask spread e g demsetz 1968 benston and hagerman 1974 and tinic 1972 among others this spread is a direct measure of the cost of liquidity when liquidity is defined hicks 1946 as the ease or rapidity with which a financial instrument can be exchanged for currency despite the importance of the bid ask spread as a liquidity measure only two studies provide evidence on splits and bid ask spreads and they yield conflicting conclusions copeland 1979 studies 162 otc firms for the period 1968 1976 and finds a statistically significant increase in percentage spreads comparing days before and after the ex date murray 1985 studies 100 otc splitting firms for the period 1972 1976 and finds no evidence of a change in percentage spreads relative to a control group

unemployment dynamics and duration dependence a major issue in the analysis of unemployment durations concerns distinguishing genuine duration dependence of the exit rate out of unemployment from unobserved heterogeneity we present a method for the nonparametric estimation of both phenomena designed to be applicable to time series data on aggregate outflows from different duration classes the model explicitly takes into account that individual exit rates are affected by the business cycle and by seasonal effects the method is applied to u s data we find diverging duration effects among black and white individuals however except for white males duration dependence is dominated by unobserved heterogeneity

on repeated moral hazard with discounting in this paper we analyze optimal contracts in an infinitely repeated agency model in which both the principal and agent discount the future we show that there is a stationary representation of the optimal contract when the agent s conditional discounted expected utility is used as a state variable this representation reduces the multi period problem to a static variational problem which can be analyzed using standard variational techniques this reduction is used to obtain several properties of the contract

on optimal unemployment compensation abstract the design of an optimal unemployment compensation scheme is analyzed using a dynamic principal agent relationship between a risk neutral planner the principal and risk averse workers the agents where the planner s inability to observe workers job search efforts creates a moral hazard problem to design an implementable scheme we require that each agent is guaranteed a minimum level of expected discounted utility regardless of his past history in contrast with previous studies we find that the optimal contract is quite close to actual unemployment compensation schemes both qualitatively and quantitatively

optimal unemployment insurance and employment history in existing unemployment insurance programmes it is standard to condition eligibility on the previous employment record of unemployed workers the purpose of this article is to study conditions under which the efficient contract exhibits these properties in order to do so we characterize the optimal unemployment insurance contract in asymmetric information environments in which workers experience multiple unemployment spells we show that if quits cannot be distinguished from layoffs it is optimal to condition the benefits paid to unemployed workers on their employment history in particular the coverage should increase with the length of previous employment spells copyright wiley blackwell

improving incentives in unemployment insurance a review of recent research abstract this paper provides a review of the recent literature on how incentives in unemployment insurance can be improved we are particularly concerned with three instruments i e the duration of benefit payments or more generally the time sequencing of benefits monitoring in conjunction with sanctions and workfare our reading of the theoretical literature is that the case for imposing a penalty on less active job search is fairly solid a growing number of empirical studies including randomized experiments are in line with this conclusion

are workers permanently scarred by job displacements this paper investigates whether workers suffer lasting scars following job displacements using david t ellwood s 1982 terminology scars represent persistent effects whereas blemishes are transitory adjustments which dissipate over time more precisely dislocated individuals are defined as scarred if they continue to earn less or to be unemployed more than their nondisplaced counterparts even after the conclusion of a several year adjustment period