book review feature public policy in an uncertain world by charles f manski cambridge ma harvard university press 2013 pp 224 39 95 isbn 978 0674066892

investor preference for large firms new evidence on economies of size in the last several decades industrial organization literature has been replete with studies demonstrating a systematic relationship between accounting rates of return and firm size in the direction of greater and more stable accounting profits for larger firms these studies have been subject to criticism for an alarming number of statistical and conceptual problems the most important of which alleges a serious bias in accounting profit measures as proxies for economic profit 2 the criticisms have resulted in a stalemate in the interpretation of empirical evidence on firm size and performance nevertheless there is continued interest in the area ostensibly resulting from policy concerns with large firm advantages in both product and capital markets this paper provides new evidence concerning the industrial organization literature controversy of the connection between firm size and performance stock market data are used to examine the relationship between capital market returns risk and firm size the findings suggest that even if there were no advantages of large size in the product market equal rates of operating profit large firms would still have a substantial capital raising advantage over small firms this advantage is unrelated to the widely recognized floatation cost economies even after controlling for nondiversifiable risk using the capital asset pricing model capm investors still demonstrate a statistically significant and economically important preference for the securities of larger firms investors apparently place a premium on large firms which is not attributable to large firms observed lower risk as captured by the widely used measure of nondiversifiable risk beta risk this finding a fresh contribution to the

what will consumers pay for social product features the importance of ethical consumerism to many companies worldwide has increased dramatically in recent years ethical consumerism encompasses the importance of non traditional and social components of a company s products and business process to strategic success such as environmental protectionism child labor practices and so on the present paper utilizes a random utility theoretic experimental design to provide estimates of the relative value selected consumers place on the social features of products

land tenure price shocks and insurgency evidence from peru and colombia abstract the paper examines how property arrangements a key determinant of rural income influence armed conflict in the presence of commodity price shocks using detailed data on district level land tenure crop produce and conflict intensity in peru and colombia estimates show that exogenous negative price shocks increase the intensity of conflict in districts with a greater presence of individual ownership relative to other types of land tenure the finding is consistent with small landowners in the export sector experiencing a sharper downturn in labor market outcomes thus reducing the opportunity cost of participating in insurgent groups

endogenous growth and the emergence of equity finance abstract this paper characterises the development of equity markets as a dynamic process that both influences and is influenced by the development of the real sector of the economy in overlapping generations economy borrowers seek funds to run risky investment projects by drawing up contracts which may take the form of either equity or debt issue in the presence of information asymmetry between borrowers and lenders the optimal contract is determined by trading off information dilution costs against bankruptcy costs significantly the equilibrium choice of contract depends on the state of the economy which in turn depends on the contracting regime based on this analysis the paper provides a theory of the joint determination of real and financial development with the ability to explain the emergence of a stock market along the path of real development

does anticipated information impose a cost on risk averse investors a test of the hirshleifer effect this paper theoretically and empirically investigates how the risk of future adverse price changes created by the anticipated arrival of information influences risk averse investors trading decisions in institutionally imperfect capital markets specifically i examine how the selling activity of individual investors immediately following an earnings announcement is influenced by the tradeoff between risk sharing benefits of immediate trade and explicit transaction costs imposed on such trades consistent with my theoretically derived predictions i find that investors current trading decisions are less sensitive to the incremental transaction costs created by short term capital gains taxes on trading profits as both the duration and intensity of the risk of future adverse price changes increase this evidence is consistent with an incremental cost to investors that results from the revelation of precise information which is commonly referred to as the hirshleifer effect

the effect of prenatal stress on cooperation evidence from violent conflict in uganda abstract are preferences endogenously determined in the womb we play a public goods game with ugandan children born during a conflict characterised by high civilian victimisation children whose caregivers suffer from post traumatic stress disorder are more likely to free ride in the game genetic and environmental factors alone do not explain the relationship but children s 2d 4d digit ratio a marker of fetal hormone exposure associated with epigenetic effects of maternal distress does our findings extend the fetal origins literature to the domain of preferences by reducing next generation s taste for cooperation conflict may have father reaching economic consequences than previously thought

behavioral rationality in finance the case of dividends as the title suggests this paper attempts to get to the specifics of the behavioral rationality theme of this conference by focusing on an area in the main core of finance namely the demand and supply of dividends where by common consent the essentially rationalist paradigm of the field seems to be limping most noticeably important and pervasive behavior patterns on both the paying and the receiving ends have despairingly been written off as puzzles even by theorists as redoubtable as fischer black see esp his much cited 1976 article behaviorists have homed in on precisely these same dividendrelated soft spots in the current body of theory see esp shefrin and statman 1984 we seem to have in sum an ideal place to look for signs of an imminent paradigm shift in the behavioral direction of precisely the kind envisioned by some of the other contributors to this conference the dividend related difficulties and supposed anomalies at issue here are more than just the parochial concern of finance specialists the dividends seem a natural area in finance where the introduction of behavioral cognitive elements might help resolve long standing anomalies particularly the seeming failure of supply to adjust to taxinduced price penalties a closer look at the empirical record however particularly at evidence of responsiveness to major structural changes shows behavior of the aggregates to be less anomalous than conventional handwringing might suggest behavioral cognitive elements whatever they might contribute to the description of particular microdecisions do not appear to be essential adjuncts to the basic finance model in the major comparative static applications for which it was intended helpful comments on an earlier version of this paper have been received from nai fu chen jean marie gagnon gur huberman kose john james poterba and especially melvin reder

what determines mutual fund trading in foreign stocks abstract we examine the portfolio rebalancing measured by the equity churn rate of mutual funds from 29 countries based on annual stockholdings over the 1999 2006 period we find that funds more often trade the stocks of companies located in countries with higher degree of information asymmetry and are less familiar to fund managers after we control for the effects of stock market development and investor protection consistent with the behavioral bias fund managers more often rebalance stocks in foreign markets that perform well this bias is exacerbated when fund managers are less familiar with and less informed about those markets

coarse thinking and persuasion we present a model of uninformative persuasion in which individuals think coarsely they group situations into categories and apply the same model of inference to all situations within a category coarse thinking exhibits two features that persuaders take advantage of i transference whereby individuals transfer the informational content of a given message from situations in a category where it is useful to those where it is not and ii framing whereby objectively useless information influences individuals choice of category the model sheds light on uninformative advertising and product branding as well as on some otherwise anomalous evidence on mutual fund advertising

fairness spillovers the case of taxation abstract it is standardly assumed that individuals react to perceived unfairness or norm violations in precisely the same area or relationship where the original offense has occurred however grievances over being exposed to injustice may have even broader consequences and also spill over to other contexts causing non compliant behavior there we present evidence that such fairness spillovers can incur large economic costs a belief that there is unfairness in taxation in the sense that the rich do not pay enough taxes is associated with a twenty percent higher level of paid absenteeism from work

high and declining prices signal product quality high and declining prices signal a high quality product high prices are the efficient means of signaling because the consequent loss of sales volume is most damaging for lower cost lower quality products as time passes and the number of informed consumers increases the signaling distortion lessens resulting in a declining price profile the prediction of high and declining prices is robust across a variety of dynamic models and is consistent with recent empirical findings copyright 1991 by american economic association

the rise of europe atlantic trade institutional change and economic growth the rise of western europe after 1500 is due largely to growth in countries with access to the atlantic ocean and with substantial trade with the new world africa and asia via the atlantic this trade and the associatedcolonialism affected europe not only directly but also indirectly by inducing institutional change where initial political institutions those established before 1500 placed significant checks on the monarchy the growth of atlantic trade strengthened merchant groups by constraining the power of the monarchy and helped merchants obtain changes in institutions to protect property rights these changes were central to subsequent economic growth

nudging and corporate environmental responsibility a natural field experiment abstract we devise a nudging natural field experiment to test the impact of a simple form of advertising on environmentally responsible products with without the increase of the responsible product price we find that the simple use of a small shelf poster explaining the importance of buying a green product with without a concurring price increase generates significant changes in market shares for some of the product classes for both food and non food products part of the effect is generated by the reduced price elasticity of consumers to the poster plus price increase treatment

investment crowding out firm level evidence from northern germany michalek j ciaian p and kancs d a investment crowding out firm level evidence from northern germany regional studies the main objective of this paper is to estimate the extent to which firm investment is substituted crowded out by investment support policies granted under the european union rural development programme rdp the empirical analyses employed the difference in difference propensity score matching approach which allows several important sources of bias to be addressed such as selection bias simultaneity bias and functional form misspecification from which many previous studies suffer using panel data of 1333 firms from the schleswig holstein region in germany it is found that the crowding out effect of the rdp is close to 100 implying that firms use public support to substitute for private investments furthermore no evidence was found that due to the rdp programme support firms would have brought forward their investments planned originally for a later period rejecting t

the consequences of child soldiering abstract little is known about the impacts of military service on human capital and labor market outcomes due to an absence of data as well as sample selection recruits are self selected screened and selectively survive we examine the case of uganda where rebel recruitment methods provide exogenous variation in conscription economic and educational impacts are widespread and persistent schooling falls by nearly a year skilled employment halves and earnings drop by a third military service seems to be a poor substitute for schooling psychological distress is evident among those exposed to severe war violence and is not limited to ex combatants

the earnings announcement premium around the globe abstract u s stocks have been shown to earn higher returns during earnings announcement months than during non announcement months we document that this earnings announcement premium exists across the globe moreover it is not isolated to a few countries of the 20 countries with enough data to conduct a within country analysis nine exhibit a significantly positive premium a cross country analysis finds that the premium is strongest in countries with the greatest increase in idiosyncratic volatility around the time of their firms earnings announcements suggesting that uncertainty over the earnings information to be disclosed is a primary driver of the global announcement premium

consumer demand for fair trade evidence from a multistore field experiment abstract we provide new evidence on consumer demand for ethical products from experiments conducted in a u s grocery store chain we find that sales of the two most popular coffees rose by almost 10 when they carried a fair trade label as compared to a generic placebo label demand for the higher priced coffee remained steady when its price was raised by 8 but demand for the lower priced coffee was elastic a 9 price increase led to a 30 decline in sales while consumers attach value to ethical sourcing there is significant heterogeneity in willingness to pay for it

the administrative foundations of self enforcing constitutions current theories of the rule of law argue that public officials respect rights if the citizens are coordinated on an equilibrium in which they collectively resist abuse constitutional rules are means to coordinate on this equilibrium in past and present states however constitutional rules often have no effect on the rule of law this paper suggests an alternative view of the origin and development of the rule of law instead of considering constitutional rules as coordination devices for citizens at large history suggests considering them as manifestations of equilibria with rulers constrained by administrators required to implement policy analysis of the administrative foundations of self enforcing constitutions may be the key to a theory and policy that would foster the rule of law in developing countries and those in transition in particular constitutional reforms might benefit from focusing on altering the equilibrium distribution of administrative capacity and power providing incentives to the administratively powerful to check predation by each other and the central authorities and to align administrators interests with social welfare

continuous time methods in finance a review and an assessment i survey and assess the development of continuous time methods in finance during the last 30 years the subperiod 1969 to 1980 saw a dizzying pace of development with seminal ideas in derivatives securities pricing term structure theory asset pricing and optimal consumption and portfolio choices during the period 1981 to 1999 the theory has been extended and modified to better explain empirical regularities in various subfields of finance this latter subperiod has seen significant progress in econometric theory computational and estimation methods to test and implement continuous time models capital market frictions and bargaining issues are being increasingly incorporated in continuous time theory the roots of modern continuous time methods in finance can be traced back to the seminal contributions of merton 1969 1971 1973b in the late 1960s and early 1970s merton 1969 pioneered the use of continuous time modeling in financial economics by formulating the intertemporal consumption and portfolio choice problem of an investor in a stochastic dynamic programming setting merton 1973b also showed how such a framework can be used to develop equilibrium asset pricing implications thereby significantly extending the asset pricing theory to richer dynamic settings and expanding the scope of applications of continuous time methods to study problems in financial economics 1 within a span of about 30 years from the publication of merton s inf luential papers continuous time methods have become an integral part of financial economics indeed in certain core areas in finance such as e g asset pricing derivatives valuation term structure theory and portfolio selection continuoustime methods have proved to be the most attractive way to conduct research and gain economic intuition the continuous time approach in these areas has produced models with a rich variety of testable implications the econometric theory for testing continuous time models has made rapid strides in the last decade and has thus kept pace with the impressive progress on the theoretical front one hopes that the actual empirical investigations and estimation using the new procedures will follow suit soon

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

computers skills and wages computer technology is most prominently used by skilled high wage workers this suggests that computer use requires skills to take full advantage of the possibilities which are particularly present among relatively skilled workers this article develops a simple technology adoption model showing that the decision to adopt computer technology depends on i the tasks to be performed ii the level of skill or education and iii the level of wages applying this model to british data it is shown that the effect of wages and particular tasks on computer adoption is larger than the effect of skills on adoption the estimates suggest that in britain computer use is likely to be a matter of cost efficiency and not so much of workers skills

reconciling conflicting evidence on the performance of propensity score matching methods there is a long standing debate in the literature over whether social programs can be reliably evaluated without a randomized experiment this paper summarizes results from a larger paper smith and todd 2001 that uses experimental data combined with nonexperimental data to evaluate the performance of alternative nonexperimental estimators the impact estimates based on experimental data provide a benchmark against which to judge the performance of nonexperimental estimators our experimental data come from the national supported work nsw demonstration and the nonexperimental data from the current population survey cps and the panel study of income dynamics psid these same data were used in influential papers by robert lalonde 1986 james heckman and joseph hotz 1989 and rajeev dehejia and sadek wahba 1998 1999 we focus on a class of estimators called propensity score matching estimators which were introduced in the statistics literature by paul rosenbaum and donald rubin 1983 traditional propensity score matching methods pair each program participant with a single nonparticipant where pairs are chosen based on the degree of similarity in the estimated probabilities of participating in the program the propensity scores more recently developed nonparametric matching estimators described in heckman et al 1997 1998a b use weighted averages over multiple observations to construct matches we apply both kinds of estimators in this paper heckman et al 1997 1998a b evaluate the performance of matching estimators using experimental data from the u s national job training partnership act jtpa study combined with comparison group samples drawn from three sources they show that data quality is a crucial ingredient to any reliable estimation strategy specifically the estimators they examine are only found to perform well in replicating the results of the experiment when they are applied to comparison group data satisfying the following criteria i the same data sources i e the same surveys or the same type of administrative data or both are used for participants and nonparticipants so that earnings and other characteristics are measured in an analogous way ii participants and nonparticipants reside in the same local labor markets and iii the data contain a rich set of variables relevant to modeling the program participation decision if the comparison group data fails to satisfy these criteria the performance of the estimators diminishes greatly more recently dehejia and wahba 1998 1999 have used the nsw data also used by lalonde to evaluate the performance of propensity score matching methods including pairwise matching and caliper matching they find that these simple matching estimators succeed in closely replicating the experimental nsw results even though the comparison group data do not satisfy any of the criteria found to be important in heckman et al 1997 1998a from this evidence they conclude that matching approaches are generally more reliable than traditional econometric estimators in this paper we reanalyze the nsw data in an attempt to reconcile the conflicting findings smith department of economics university of western ontario social science centre london on n6a 5c2 canada and nber todd department of economics university of pennsylvania 3718 locust walk philadelphia pa 19104 and nber versions of the paper that is the source for this paper have been presented at a 2000 meeting of the institute for research on poverty in madison wisconsin at the western research network on employment and training summer workshop august 2000 at the canadian international labour network meetings september 2000 and at the university of north carolina we thank james heckman for comments on this paper and we thank robert lalonde for comments and for providing us with the data from his 1986 study we thank rajeev dehejia for providing us with information helpful in reconstructing the samples used in the dehejia and wahba 1998 1999 studies jingjing hsee and miana plesca provided excellent research assistance

the wto trade effect this paper reexamines the gatt wto membership efiect on bilateral trade ows using nonparametric methods including pair matching permutation tests and a rosenbaum 2002 sensitivity analysis together these methods provide an estimation framework that is robust to misspeciflcation biases allows general forms of heterogeneous treatment efiects and addresses potential hidden selection biases this is in contrast to most conventional parametric studies on this issue our results suggest large gatt wto trade promoting efiects robust to various restricted matching criteria alternative indicators for gatt wto involvement different matching methodologies non random incidence of positive trade ows and inclusion of multilateral resistance terms

heterogeneous sports participation and labour market outcomes in england based on a unique composite dataset measuring heterogeneous sports participation labour market outcomes and local facilities provision this article examines for the first time the association between different types of sports participation and employment and earnings in england clear associations between labour market outcomes and sports participation are established through matching estimation while controlling for some important confounding factors the results which are supplemented and supported by a formal sensitivity analysis suggest a link between different types of sports participation to initial access to employment and then higher income opportunities with ageing however these vary between the genders and across sports specifically the results suggest that team sports contribute most to employability but that this varies by age across genders and that outdoor activities contribute most towards higher incomes

misspecification of capital asset pricing this study documents empirical anomalies which suggest that either the simple one period capital asset pricing model capm is misspecified or that capital markets are inefficient in particular portfolios based on firm size or earnings price e p ratios experience average returns systematically different from those predicted by the capm furthermore the abnormal returns persist for at least two years this persistence reduces the likelihood that these results are being generated by a market inefficiency rather the evidence seems to indicate that the equilibrium pricing model is misspecified however the data also reveals that an e p effect does not emerge after returns are controlled for the firm size effect the firm size effect largely subsumes the e p effect thus while the e p anomaly and value anomaly exist when each variable is considered separately the two anomalies seem to be related to the same set of missing factors and these factors appear to be more closely associated with firm size than e p ratios

stress testing the equity home bias a turnover analysis of eurozone markets abstract shifts in equity turnover happen on and around holidays because rationally bounded investors become distracted their pattern reveals a persistent equity home bias even in the eurozone a stress test case for the survival of this bias given the high level of economic and financial development and integration in this area the bias is greater for small caps because investors are reluctant to hold this class of foreign asset our study corroborates calendar anomalies in trading volumes but refutes the hypothesis regarding turnover sensitivity to stock returns common in the empirical and theoretical literature based on investor heterogeneity and short sale constraints our results reveal vanishing cost asymmetries in taking long rather than short positions

evaluating the econometric evaluations of training programs with experimental data this paper takes the results of an employment and training program thatwas run as a field experiment in which the participants were randomlyassigned into a treatment or a control group and compares these results to the estimates that might have been produced by an econometrician who evaluated the program using the same econometric procedures that have been used in the program evaluation literature this comparison shows that many of these econometric procedures fail toreplicate the experimentally determined results and suggests that researchers should be aware of the potential for specification errorsin other nonexperimental evaluations copyright 1986 by american economic association

expert opinion and the demand for experience goods an experimental approach in the retail wine market abstract the effect of expert opinion on demand for experience goods is difficult to quantify as the relationship between purchases and reviews may be driven by product quality further it is unclear whether a review based demand effect is due to providing quality or existence information using a retail field experiment to overcome these obstacles we find a significant positive average consumer response to expert opinion labels for wine demand decreases for low scoring wines and increases for wines scoring average or higher results indicate that expert opinion labels transmit quality information as opposed to solely shelf visibility

the ability of global stock exchange mechanisms to mitigate home bias evidence from euronext this paper examines the effects on equity home bias of two mechanisms adopted by euronext when it was formed by the merger of four european countries stock exchanges in 2002 the two structural mechanisms are the integration of trading platforms across the four predecessor exchanges and the creation of named segments of the integrated exchange on which firms could voluntarily list by precommitting to enhanced disclosure and transparency employing a difference in differences research design using other european union companies as a control group we document that the integration of the euronext market was associated with a reduction in home bias for firms listed on the named segments of the euronext exchange but not for the nonsegment euronext firms our results suggest that the reduction in transaction costs from the integration of the trading platforms did not make the nonsegment euronext firms more attractive to the specific investors for whom the transaction costs were reduced on the other hand the decrease in information costs due to the precommitments to enhanced transparency made the segment firms more attractive to all categories of foreign investors consistent with the information costs hypothesis this paper was accepted by mary barth accounting

capital market equilibrium with externalities production and heterogeneous agents abstract the paper studies general equilibrium in an economy with externalities production and heterogeneous agents the model developed builds on brock brock w a 1982 asset prices in a production economy in mccall j j ed the economics of information and uncertainty university of chicago press chicago pp 1 43 and merton merton r c 1987 a simple model of capital market equilibrium with incomplete information journal of finance 42 483 510 it involves both a stock market and a market for loans together with negative externalities produced by a subset of firms importantly the technological production structure of the firms is reflected in the properties of the shares traded in the stock market agents are heterogeneous in their financial choices potentially discriminating against the firms producing a negative externality the model sheds light on the utility costs of the discriminating behavior and on the impact on the price of the stock issued by the firm which is responsible for the externality the model is used to study the factors which may magnify or reduce the impact of discrimination a set of discriminated firms may be seriously affected only if the discriminating investors command a large portion of overall wealth and or they do not represent important diversification instruments the model can be applied to understanding the effects of socially responsible investment whereby investors discriminate against companies belonging to some sectors which are perceived as socially dangerous or unethical

charity as a substitute for reputation evidence from an online marketplace consumers respond positively to products tied to charity particularly from sellers that are relatively new and hence have limited alternative means for assuring quality we establish this result using data from a diverse group of ebay sellers who experiment with charity by varying the presence of a donation in a set of otherwise matched product listings most of charity s benefits accrue to sellers without extensive ebay histories consistent with charity serving as a quality signal we find fewer customer complaints among charity intensive sellers

optimal stock trading with personal taxes implications for prices and the abnormal january returns abstract the tax law confers upon the investor a timing option to realize capital losses and defer capital gains with the tax rate on long term gains and losses being about half the short term rate the law provides a second timing option to realize losses short term and gains long term if at all our theory and simulation over the 1962 1977 period establish that taxable investors should realize long term gains in high variance stocks and repurchase stock in order to realize potential future losses short term tax trading does not explain the small firm anomaly but predicts a seasonal pattern in trading volume which maps into a seasonal pattern in stock prices the january anomaly only if investors are irrational or ignorant of the price seasonality

the countervailing effects of competition on public goods provision when bargaining inefficiencies lead to bad outcomes political competition is widely recognized as a mediator of public goods provision through its salutary effect on incumbents electoral incentives we argue that political competition additionally mediates public goods provision by reducing the efficiency of legislative bargaining these countervailing forces may produce a net negative effect in places with weak parties and low transparency typical of many young democracies we provide evidence of a robust negative relationship between political competition and local public goods using panel data from mali tests of mechanisms corroborate our interpretation of this relationship as evidence of legislative bargaining inefficiencies to explore the generalizability of these findings we analyze cross country panel data and show that political competition leads to better worse public goods provision under high low levels of party system institutionalization the paper sheds light on why political competition is only selectively beneficial and underscores the importance of considering both the electoral and legislative arenas

sustainability labels on coffee consumer preferences willingness to pay and visual attention to attributes abstract sustainability labels are important tools that help consumers assess the sustainability aspects of food while past studies have focused on visual attention to nutrition information no study has investigated the visual attention paid by consumers to the sustainability information on food our study contributes to the need to better understand consumers attention to sustainability information when making food choices the objective was to explore the importance that consumers attach to sustainability attributes and investigate how this relates to the visual attention paid to these attributes during the choice decision and to willingness to pay wtp visual attention during the decision making process was measured in terms of fixation time and fixation count which were then analyzed in relation to the stated attribute importance our results suggest that consumer segments with differences in stated attribute importance visually attend differently to these attributes higher valued attributes also exhibited higher visual attention our results suggest that consumers who spend more time attending to and fixate more on sustainability attributes value them more

rollover hedging and missing long term futures markets sequential rollover of annual futures positions provides farmers or others with a means of long term hedging consequently the absence of multiyear futures markets may not be a serious problem however year to year basis risk exists which can render rollovers ineffective in hedging evidence on soybean corn and cotton futures suggests that rollovers would be effective at locking in an initial price for a three to six year period but would be ineffective in routine hedging over a series of successive three to six year periods

disaster aid and preferences the long run impact of the tsunami on giving in sri lanka summary do natural disasters produce effects on preferences of victims in the long run we test the impact of the tsunami shock on generosity of a sample of sri lankan affected unaffected microfinance borrowers seven years after the event specifically we test the effect of the shock at the extensive margin by comparing damaged with non damaged individuals in terms of giving and expected giving in a dictator game moreover at the intensive margin we compare the participants based on the amount of damage experienced and recovery aid received the advantage of this last comparison is that differences in observables between the groups are minimized we reduce further identification problems by selecting a random sample of damaged and non damaged borrowers belonging to the same microfinance organization who are therefore likely to share some important common traits that are usually unobservable to researchers we complete our identification strategy with weighted least squares instrumental variable estimates and a sensitivity analysis on the exogeneity assumption the main findings of the paper support the hypothesis that the shock affects participants preferences in the long run first the tsunami negatively affects generosity at the extensive margin as those who suffered at least one damage give and expect less than those who did not second while large recovery assistance does not directly affect giving and expected giving it increases especially the latter indirectly i e when interacted with the number of damages our results reconcile that part of the literature showing evidence of natural shocks having a detrimental effect on social preferences fleming chong alberto bejarano 2011 cassar grosjean whitt 2013 with that supporting instead a positive link solnit 2009 whitt wilson 2007 cassar healy von kessler 2011 furthermore since our study focuses on the long run impact of a natural disaster previous results on short run effects are not necessarily inconsistent with ours

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

an empirical analysis of the relationship between brand loyalty and consumer price elasticity this empirical paper explores the relationship between consumer brand preference or loyalty and price elasticity in purchase behavior this behavior is conceptualized as resulting from two distinct but related decisions namely a brand choice decision and a purchase quantity decision we argue that loyal consumers will be less price sensitive in the choice decision than nonloyal consumers however this direction is expected to be reversed in the quantity decision with loyal consumers expected to be more price sensitive than nonloyal consumers we model the choice and quantity decisions jointly using the limited dependent variable framework described in krishnamurthi and raj the data used are diary panel data on a frequently purchased product class from burke and caffeinated ground coffee scanner data from iri we show that loyals are less price sensitive than nonloyals in the choice decision but more price sensitive in the quantity decision managerial implications of the differing elasticities are disc

some recent developments in futures hedging the use of futures contracts as a hedging instrument has been the focus of much research at the theoretical level an optimal hedge strategy is traditionally based on the expected utility maximization paradigm a simplification of this paradigm leads to the minimum variance criterion although this paradigm is quite well accepted alternative approaches have been sought at the empirical level research on futures hedging has benefited from the recent developments in the econometrics literature much research has been done on improving the estimation of the optimal hedge ratio as more is known about the statistical properties of financial time series more sophisticated estimation methods are proposed in this survey we review some recent developments in futures hedging we delineate the theoretical underpinning of various methods and discuss the econometric implementation of the methods

food labeling and eco friendly consumption experimental evidence from a belgian supermarket using an incentive compatible framed field experiment we investigate whether consumers food consumption is more eco friendly when the information about a product s environmental impact is more easily accessible through an online survey we identify a food label that is perceived to be the most easily accessible for assessing a product s eco friendliness among six alternatives these alternatives vary on multiple dimensions including whether a standardized score of the overall environmental impact is added this new food label is subsequently tested in an experimental food market embedded in a belgian supermarket we find that the presence of the new label that was preselected in the online survey leads to more eco friendly food consumption relative to either the label currently used in the supermarket or the label that contains the raw information of the environmental impact in our experimental food market the use of an easy to interpret but comprehensive environmental information label increases the overall eco friendliness of our subjects food consumption by about 5 3 relative to the default label used in current markets

price convexity and skewness this paper develops a model in which investors who are prohibited from short selling agree to disagree on the precision of a publicly observed signal the model implies that the equilibrium price is a convex function of the public signal the model predicts that 1 the stock price reacts more to good news than to bad news 2 the skewness of stock returns is positively correlated with contemporaneous returns but negatively correlated with lagged returns 3 short sale constraints increase rather than decrease skewness and 4 disagreement about information precision increases skewness empirical tests conducted find supportive evidence for all these predictions

the impact of climate information on milk demand evidence from a field experiment it has been suggested that carbon labelling of food on voluntary or non voluntary basis could reduce emissions of greenhouse gases however there is limited empirical evidence on the influence of such labels on consumer purchases the purpose of this study was to investigate whether voluntary carbon labelling affects the demand for milk a randomized field experiment was conducted in 17 retail stores in sweden where a sign provided consumers with qualitative information about the carbon impact of climate certified milk the results suggest that the sign increased the demand for the climate certified milk by approximately 6 8 and the result is robust to alternative model specifications the effect is entirely driven by large stores such as supermarkets we find no statistically significant impact on total milk sales and the dataset is too small to verify the consequences for other milk brands the effect on the demand for the labelled milk is short lived

war and conflict in economics theories applications and recent trends we review the main economic models of war and conflict these models vary in details but their implications are qualitatively consistent highlighting key commonalities across a variety of conflict settings recent empirical literature employing both laboratory and field data in many cases confirms the basic implications of conflict theory however this literature also presents important challenges to the way economists traditionally model conflict we finish our review by suggesting ways to address these challenges

financial asset holdings and political attitudes evidence from revolutionary england the english parliament s struggle for supremacy against monarchical dictatorship during the civil war 1642 1648 was crucial for the establishment of representative government yet its lessons continue to be debated i exploit novel data on individual mps drawn from 1 842 biographies to show that the conflict was over overseas interests and other factors over which the executive enjoyed broad constitutional discretion rather than over domestic property rights i further exploit the coincidence of individual mps ability to sign legally binding share contracts with novel share offerings by overseas companies to measure the effect of overseas share investment on their political attitudes i show that overseas shareholding pushed moderates lacking prior mercantile interests to support reform i interpret the effect of financial assetholding as allowing new investors to exploit emerging economic opportunities overseas aligning their interests with traders by consolidating a broad parliamentary majority that favored reform the introduction of financial assets also broadened support for the institutionalization of parliamentary supremacy over dictatorial rule jel codes o10 g11 f10 k00 n23 p10

household portfolio diversification a case for rank dependent preferences the proliferation of novel preference theories in financial economics is hampered by a lack of non experimental evidence and by the theories additional complexity which has not been shown to be critical in applications in this article i present arguments in support of preferences with rank dependency using the survey of consumer finances data i document two widespread patterns inconsistent with expected utility i many households simultaneously invest in well deversified funds and in poorly diversified portfolios of stocks and ii some households with substantial savings do not invest anything in equities i show that portfolio choice models with rank dependent preferences plausibly parameterized and under fully rational assumptions are quantitatively consistent with the observed diversification these results call for further efforts to integrate the models of rank dependent preferences in portfolio theory and asset pricing the decision theoretic literature has long acknowledged the shortcomings of the expected utility theory of von neumann and morgenstern 1944 several generalizations of the theory are inspired by the experimental evidence and aimed at improving its descriptive accuracy however there are few applications of new models of preferences in finance and expected utility continues to dominate the field 1 two principal hurdles slow the proliferation of novel preferences in financial economics first the lack of empirical non experimental or field data confirming that the behavior motivating non expected utilities is widespread outside the laboratory settings second the additional and often significant complexity of the alternative preferences which has not been shown to be critical in applications where the models based on expected utility fall short of reasonable predictions this article presents empirical and theoretical this paper was previously circulated under the title household portfolio diversification the paper has benefited from the comments of shlomo benartzi luca benzoni markus brunnermeier john dickhaut maria perozek raj singh hersh shefrin and workshop participants at minnesota finance bag lunch 2003 wharton conference household financial decision making and portfolio choice and 2003 summer meetings of econometric society i would like to thank cam harvey the editor and an anonymous referee for many helpful comments and suggestions a special thanks to jack kareken for comments and editorial help on an earlier draft i am grateful to donna zerwitz for editorial assistance the views expressed herein are those of the author and not necessarily of the federal reserve bank of minneapolis or the federal reserve system all errors and omissions are the sole responsibility of the author address correspondence to valery polkovnichenko finance 3 122 csom 319 19 th

financial system design and liquidity provision by banks and markets in a dynamic economy this paper contributes to the literature on financial system design by comparing markets and banks in a dynamic economy investors trade off their liquidity needs against the high returns on illiquid investments both the banking system and the market can provide partial liquidity insurance to investors we consider full market participation as well as limited market participation we demonstrate that the full participation market with intergenerational trading can provide more liquidity than one without insurance is provided through wealth transfer across generations instead of cross subsidization across contemporaneous types as is the case in the finite economy given a full participation market that allows trading across generations only banks with initial capital can provide additional liquidity in a limited participation market with uncertainty about trading types an intergenerational bank with or without initial capital provides additional insurance to investors the need for trade is eliminated finally if there is no uncertainty about trading types then an intergenerational bank with initial capital eliminates the need for trading and improves welfare for all an intergenerational bank without initial capital improves welfare for people who do not trade

can risk averse households make risky investments the role of trust in others in this paper using data from the survey on health ageing and retirement in europe share 2006 and 2013 waves we illustrate the link between individuals attitudes to financial risk combined with their willingness to trust others and their investments in risky assets individuals who display either risk tolerance alone or to a lesser extent risk aversion and trust more frequently decide to buy risky assets the comparison between scandinavian and mediterranean countries indicates that trust plays qualitatively different roles depending on the prevailing combination of risk attitude and trust in the area being studied

differential information and security market equilibrium we propose a simple model of equilibrium asset pricing in which there are differences in the amounts of information available for developing inferences about the returns parame ters of alternative securities in contrast with earlier work we show that parameter uncer tainty or estimation risk can have an effect upon market equilibrium under reasonable conditions securities for which there is relatively little information are shown to have relatively higher systematic risk when that risk is properly measured ceteris paribus the initially very limited model is shown to be robust with respect to relaxation of a number of its principal assumptions we provide theoretical support for the empirical examination of at least three proxies for relative information period of listing number of security returns observations available and divergence of analyst opinion

are they efficient in the middle using propensity score estimation for modeling middlemen in indian corporate corruption corrupt regulatory environment encourages firms to deploy middlemen for speedy and assured acquisition of different services from regulatory agencies using a world bank dataset of 2210 indian manufacturing firms this article examines how firms with middlemen deal with corrupt governmental agencies for its operational efficiency our results demonstrate that deployment of middlemen by the firms is often accompanied by a substantial increase in operational delay relatively trigger more consumption of senior management s time on regulatory disentanglement enhance the likelihood tendency to pay bribe and likely to face more court cases as a means of restitution of legal rights as firm specific attributes may contaminate our preliminary results we utilized the propensity score framework to examine relationships among variables of interests our study contributes to the inconspicuous part of the corruption literature by attempting to present a comprehensive but indirect assessment of the functions of middlemen that predominantly remained unattended except some scattered descriptive case based anecdotal presentations

does home bias affect firm value evidence from holdings of mutual funds worldwide this study finds strong evidence that home bias affects firm valuation at both country and firm levels at the country level increasing the bias of domestic investors toward home equity lowers the market valuation of home equity at the firm level firm value increases as the compositions of local equities held by domestic and foreign investors tend toward the firms global market capitalization weights but decreases as their weights deviate from global weights overall the evidence is consistent with the optimal global risk sharing hypothesis that the greater risk sharing between domestic and foreign investors in international capital markets reduces the cost of capital and hence enhances market valuation

the effects of market segmentation and investor recognition on asset prices evidence from foreign stocks listing in the united states non u s firms cross listing shares on u s exchanges as american depositary receipts earn cumulative abnormal returns of 19 percent during the year before listing and an additional 1 20 percent during the listing week but incur a loss of 14 percent during the year following listing we show how these unusual share price changes are robust to changing market risk exposures and are related to an expansion of the shareholder base and to the amount of capital raised at the time of listing our tests provide support for the market segmentation hypothesis and merton s 1987 investor recognition hypothesis the globalization of u s capital markets has accelerated dramatically in the past decade increasing numbers of companies from overseas have chosen to either raise capital through global equity issues or prepare for future capital raising by way of cross listings on u s exchanges as of 1997 about 1 300 non u s companies have listed their shares for trading on the new york stock exchange nyse the american exchange amex the national association of securities dealers automation quotation nasdaq system or

engel curves for fair trade consumption and development perspectives for producers evidence from data on real fairtrade purchases while fairtrade sales have exhibited two digit growth rates over recent decades their capacity to become large enough to generate substantial gains for producers is still uncertain estimating fai

localized knowledge spillovers and patent citations a distance based approach abstract we develop a new distance based test of localized knowledge spillovers that embeds the concept of control patents using microgeographic data we identify localization distance for each te

a signaling explanation for charity this article examines a novel but plausible motive for charitable giving charitable donations which are observable can signal wealth or income the signaling equilibrium of charitable donations has attractive properties donations increase proportionally with population size governmental funding for public goods affects private charity only through an income effect crowding out need not be complete income redistribution is generically nonneutral increasing the spread between the poorest and richest person in a community tends to increase private donations our theory are based on the assumption that people are willing to make charitable donations even if they will not increase provision of the public good the data on charitable giving support the hypothesis that donors donate at least partly for signaling purposes rather than only to aid the recipient or to obtain satisfactions unrelated to status though charitable organizations usually report donations within categories thus not allowing perfect revelation for analytical tractability we shall consider an equilibrium with perfect revelation and a continuum of types as characterized in george j mailath 1987 and norman j ireland 1994

rethinking economic development i provide a summary reflection and assessment of the current state of economic development in both the policy and academic worlds in terms of development policy currently the primary focus is on policy interventions namely foreign aid aimed at fixing the deficiencies of developing countries academic research also has a similar focus except with an emphasis in rigorous evaluation of interventions to estimate causal effects a standard set of versatile quantitative tools is used e g experimental and quasi experimental methods which can be easily applied in a range of settings to estimate the causal effects of policies which are typically presumed to be similar across contexts in this article i take a step back and ask whether the current practices are the best that we can do are foreign aid and policy interventions the best options we have for poverty alleviation what else can be done is our current research strategy characterized by rigorous but a lack of context specific analysis the best method of analysis is there a role for other research methods for a deeper understanding of the local context and for more collaboration with local scholars repenser le developpement economiquee dans cet article je propose un apercu une reflexion et une evaluation de l etat actuel du developpement economique a la fois dans les spheres politiques et universitaires en matiere de developpement economique l attention est principalement portee sur l intervention politique c est a dire l aide exterieure visant a corriger les defaillances des pays en developpement les recherches universitaires y portent une attention similaire mais en mettant davantage l accent sur l evaluation rigoureuse de ces memes interventions pour en mesurer les effets de causalite a cette fin un ensemble d outils quantitatifs et modulables standard sont utilises notamment par l entremise de methodes experimentales et quasi experimentales pouvant facilement s appliquer a une vaste gamme de situations et ce aux fins d evaluations des liens de causalite engendres par ces politiques liens habituellement consideres comme similaires d un contexte a l autre dans cet article je prends un peu de recul pour m interroger sur la pertinence des pratiques actuelles les interventions politiques et l aide exterieure offrent elles les meilleures options pour reduire la pauvrete que pouvons nous faire d autre notre strategie de recherche actuelle caracterisee par des analyses rigoureuses mais peu adaptees a des contextes specifiques est elle la meilleure d autres methodes de recherche peuvent elles permettre de mieux comprendre les contextes regionaux et favoriser une meilleure collaboration avec les intellectuels locaux

optimal price policy and the futures markets abstract because of the short term nature of existing commodity futures contracts optimally hedged producers remain subject to intertemporal income uncertainty but price stabilization may be detrimental because it negates the benefits of intertemporal production flexibility multiperiod futures would be preferred to price stabilization although they would not provide perfect hedging opportunities thus leaving scope for government intervention the optimal price policy requires the support price to be positively correlated to the futures price that prevails when production decisions are made

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

informal care and long term labor market outcomes in this paper we estimate long run effects of informal care provision on female caregivers labor market outcomes up to eight years after care provision we compare a static version where average effects of care provision in a certain year on later labor market outcomes are estimated to a partly dynamic version where the effects of up to three consecutive years of care provision are analyzed our results suggest that there are significant initial negative effects of informal care provision on the probability to work full time the reduction in the probability to work full time by 4 percentage points or 2 4 5 0 if we move from point to partial identification is persistent over time short run effects on hourly wages are zero but we find considerable long run wage penalties

who governs socially oriented voluntary sustainability standards not the producers of certified products summary voluntary sustainability standards setting organizations vsssos create standards to improve the social and or environmental impacts of globalized production networks vsssos are often assumed to have multi stakeholder governance structures that include the producers of certified products e g farmers artisans and workers this article argues that including producers in governance is desirable however analysis of 33 vsssos constitutions shows two thirds do not even imply intention to include producers at most 25 ensure producers have votes seats and 18 give producers veto power the discussion examines what is lost when vsssos do not bring traditionally marginalized voices to global economic governance

the decomposition of promotional response an empirical generalization price promotions are used extensively in marketing for one simple reason consumers respond the sales increase for a brand on promotion could be due to consumers accelerating their purchases i e buying earlier than usual and or buying more than usual and or consumers switching their choice from other brands purchase acceleration and brand switching relate to the primary demand and secondary demand effects of a promotion gupta 1988 captures these effects in a single model and decomposes a brand s total price elasticity into these components he reports for the coffee product category that the main impact of a price promotion is on brand choice 84 and that there is a smaller impact on purchase incidence 14 and stockpiling 2 in other words the majority of the effect of a promotion is at the secondary level 84 and there is a relatively small primary demand effect 16 this paper reports the decomposition of total price elasticity for 173 brands across 13 different product categories on average we find that 25 of the elasticity is due to primary demand expansion i e purchase acceleration and 75 to secondary demand effects or brand switching thus while gupta s finding that the majority of promotional response stems from brand switching is supported the average magnitude of the effect appears to be smaller than first thought more important there is ample evidence that promotions have a significant primary demand effect the relative emphasis on purchase acceleration and brand switching varies systematically across categories and the second goal of the paper is to explain this variation as a function of exogeneous covariates in doing this we recognize that promotional response is the consumer s reaction to a price promotion and therefore develop a framework for understanding variability in promotional response that is based on the consumer s perspective of the benefits from a price promotion these benefits are posited to be a function of i category specific factors ii brand specific factors and iii consumer characteristics the framework is formalized as a generalized least squares meta analysis in which the brand s price elasticity is the dependent variable several interesting results emerge from this analysis category specific factors brand specific factors and consumer demographics explain a significant amount of the variance in promotional response for a brand at both the primary and secondary demand levels category specific factors have greater influence on variability in promotional response and its decomposition than do brand specific factors there are several instances where exogenous variables do not affect total elasticities yet significantly affect individual components of total elasticity in fact the lack of a significant relationship between the variables and total elasticity is often due to offsetting effects within two or more of the three behavioral components of elasticity this is particularly true for brand specific factors which typically have no effect on total elasticity yet have important effects on the individual behaviors there is some evidence to suggest that not all promotion related increases in primary demand are due to forward buying in some cases promotions appear to increase consumption we use these results to illustrate how category and brand specific factors work to drive primary and secondary demand elasticities in different directions in short this paper offers an empirical generalization of a key finding on promotional response how elasticities decompose across brand choice purchase incidence and stockpiling and new insights into factors that explain variance in promotional response these findings are likely to be of interest to researchers who are concerned with theory development and the generalizability of marketing phenomena and to managers who plan promotion campaigns

more possessions more worry abstract a common wisdom asserts that the wider the universe of assets to choose from the greater the investor s welfare we show that this is not the case in practice where parameters have to be estimated even when the estimates are unbiased surprisingly risk aversion plays a crucial role corresponding to the desirability of asset expansion by dividing investors in three groups investors with very low risk tolerance and investors with very high risk tolerance are better off with asset expansion and investors with moderate risk tolerance are worse off despite the option to refrain from investing in the additional asset

the political economy of financial regulation evidence from u s state usury laws in the 19th century financial regulation was as hotly debated a political issue in the 19th century as it is today we study the political economy of state usury laws in 19th century america exploiting the wide variation in regulation enforcement and economic conditions across states and time we find that usury laws when binding reduce credit and economic activity especially for smaller firms we examine the motives of regulation and find that usury laws coincide with other economic and political policies favoring wealthy political incumbents particularly when they have more voting power the evidence suggests financial regulation is driven by private interests capturing rents from others rather than public interests protecting the underserved we examine the motives and consequences of financial regulation to better understand the implications of regulation for financial development and economic growth while the current global financial crisis has reinvigorated the debate on financial regulation s effects and motives there is a long history of financial regulation and development we can examine to shed light on these issues specifically we study the political economy of financial regulation and its consequences through the lens of usury laws in 19th century america usury laws are arguably the oldest form of financial regulation mentioned in both the bible and the koran and dating back to ancient rome having long been

using experiments to evaluate performance standards what do welfare to work demonstrations reveal to welfare reformers this paper examines how experimental demonstrations can be used to inform planners about the efficacy of social programs in light of a performance standard the problem is illustrated by considering the situation faced by state governments attempting to design programs to meet the new federal welfare to work standards data from experimental evaluations alone allow only limited inferences about the labor market outcomes of welfare recipients combined with prior information on the selection process however these data are informative suggesting either that the long run federal requirements cannot be met or that these standards will only be met under special circumstances

private or public school advantage evidence from 40 countries using pisa 2012 mathematics abstractit is known that in most countries private school students outperform students in public schools in international assessments however the empirical literature recognizes that assessing the true effect of private school attendance requires addressing selection and sorting issues on both observabland unobservables the existing empirical evidence on the private school effect mostly covers oecd and latin american countries with little evidence on other parts of the world there is recent emerging country specific evidence doubting the existence of a private school advantage i use pisa 2012 data for mathematics and two different methodologies to derive baseline and bias corrected estimates of the private dependent and independent school effect for 40 countries a robust private school advantage is found only in a handful of countries public schools generally perform as well as private subsidized schools and outperform independent schools accounting for both peer effects and selection is necessa