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on Experimental Economics |
| By: | Astrid Matthey (Max Planck Institute of Economics, Strategic Interaction Group, Jena, Germany); Tobias Regner (Max Planck Institute of Economics, Strategic Interaction Group, Jena, Germany) |
| Abstract: | In experimental economics there exists a lively debate about the independence of observations. Although opinions on the issue differ widely, all concerns regard the independence of subjects' behavior within one session or experiment. This paper attempts to shed some light on the independence of observations between experiments, if they are generated by the same subjects. We analyze experiments with an allocation decision and find that participation in previous experiments tends to increase the amount subjects allocate to themselves. Hence, independence between experiments cannot be presumed if subjects participate repeatedly. The finding has implications for the interpretation of previous allocation decision results and deserves attention when running future experiments. |
| Keywords: | experimental methods, independence of observations, social preferences, conditional cooperation |
| JEL: | C90 D84 |
| Date: | 2009–09–25 |
| URL: | http://d.repec.org/n?u=RePEc:jrp:jrpwrp:2009-074&r=exp |
| By: | Werner Güth (Max Planck Institute of Economics); M. Vittoria Levati (Max Planck Institute of Economics); Matteo Ploner (Max Planck Institute of Economics) |
| Abstract: | We study ultimatum and dictator experiments where the first mover chooses the amount of money to be distributed between the players within a given interval, knowing that her own share is ?xed. Thus, the first mover is faced with scarcity, but not with the typical trade-off between her own and the other's payoff. Removing the trade-off inspires significant generosity, which is not affected by the second mover's veto power. On the whole our results con?rm heterogeneity in behavior, but point to efficiency concerns as the predominant motive. |
| Keywords: | Ultimatum, Dictator, Social Preferences |
| JEL: | C70 C91 D63 |
| Date: | 2009–09–25 |
| URL: | http://d.repec.org/n?u=RePEc:jrp:jrpwrp:2009-071&r=exp |
| By: | Giuseppe Attanasi, Luca Corazzini, Nikolaos Georgantzis, Francesco Passarelli. |
| Abstract: | We study, both theoretically and experimentally, the relation between preferred majority thresholds and behavioral traits such as the degree of risk aversion and the subjective confidence on others' preferences over the alternatives to vote. The main theoretical findings are supported by experimental data. The majority threshold chosen by a subject is positively and significantly correlated with her degree of risk aversion while it is negatively and significantly associated to her confidence on others' votes. Moreover, in a treatment in which each subject can privately observe the distribution of preferences over a sub-group of participants, we find that the quality of information crowds-out subject's confidence. |
| Keywords: | majority threshold, risk aversion, (over-)confidence, laboratory experiment. |
| JEL: | C91 D72 H11 D81 |
| Date: | 2009–10 |
| URL: | http://d.repec.org/n?u=RePEc:slp:islawp:islawp34&r=exp |
| By: | Sabrina Teyssier (Thurgau Institute of Economics, Kreuzlingen, Switzerland; University of Konstanz, Department of Economics, Germany) |
| Abstract: | This paper analyzes which type of intrinsic preferences drive an agent’s behavior in a sequential public good game depending on whether the agent is ï¬rst or second mover. Theoretical predictions are based on heterogeneity of individuals in terms of social and risk preferences. We modelize preferences according to the inequity aversion model of Fehr and Schmidt (1999) and to the assumption of constant relative risk aversion. Risk aversion is signiï¬cantly and negatively correlated with the contribution decision of ï¬rst movers. Second movers with sufficiently high advantageous inequity aversion free-ride less and reciprocate more than others. Both results are predicted by our model. Nevertheless, no effect of disadvantageous inequity aversion of ï¬rst movers is found in the data while theory predicted it. Our results underline the importance of taking into account the order of agents’ play to correctly understand which type of preferences influences cooperation in voluntary contribution mechanisms. They suggest that individuals’ behavior can be consistent between different experimental games. |
| Keywords: | inequity aversion, risk aversion, public good game, conditional contribution |
| JEL: | C72 C91 D63 D81 H41 |
| Date: | 2009 |
| URL: | http://d.repec.org/n?u=RePEc:gat:wpaper:0919&r=exp |
| By: | Sandra Ludwig (University of Munich); Christina Strassmair (University of Munich) |
| Abstract: | Is free-riding in teams reduced when one member receives a signal on his colleagueís performance? And how does free-riding depend on the signal's type? We address these questions in experimental teams in which two agents sequentially exert effort to contribute to the team output. We vary the type of information the second mover receives prior to his effort choice and find that agents work more when signals are available. Overall, behavior differs from predictions of standard theory. Signals that are predicted to have no effect are, in fact, influential and signals that are predicted to have an effect are redundant. |
| Keywords: | Team production, Free-riding, Experiment, Information, Signal |
| JEL: | C92 J30 M50 D82 |
| Date: | 2009–09 |
| URL: | http://d.repec.org/n?u=RePEc:trf:wpaper:277&r=exp |
| By: | Stefan Bauernschuster (University of Jena); Jörg Oechssler (Department of Economics, University of Heidelberg, Germany); Peter Duersch (University of Heidelberg); Radovan Vadovic (ITAM, Mexico City) |
| Abstract: | The question whether a minimum rate of sick pay should be mandated is much debated. We study the effects of this kind of intervention in an experimental labor market that is rich enough to allow for moral hazard, adverse selection, and crowding out of good intentions to occur. We find that higher sick pay is reciprocated by workers through higher effort but only if sick pay is not mandated. We also study adverse selection effects when workers have different probabilities of getting sick and can reject the hypothesis that this leads to market breakdown. Overall, we find that mandating sick pay actually leads to a higher voluntary provision of sick pay by ?rms. |
| Keywords: | sick pay, sick leave, experiment, gift exchange |
| JEL: | J3 C7 C9 |
| Date: | 2009–09–25 |
| URL: | http://d.repec.org/n?u=RePEc:jrp:jrpwrp:2009-076&r=exp |
| By: | Butler, Jeffrey V. (Einaudi Institute for Economics and Finance); Giuliano, Paola (University of California, Los Angeles); Guiso, Luigi (European University Institute) |
| Abstract: | A vast literature has investigated the relationship between trust and aggregate economic performance. We investigate the relationship between individual trust and individual economic performance. We find that individual income is hump-shaped in a measure of intensity of trust beliefs available in the European Social Survey. We show that heterogeneity of trust beliefs in the population, coupled with the tendency of individuals to extrapolate beliefs about others from their own level of trustworthiness, could generate the non-monotonic relationship between trust and income. Highly trustworthy individuals think others are like them and tend to form beliefs that are too optimistic, causing them to assume too much social risk, to be cheated more often and ultimately perform less well than those who happen to have a trustworthiness level close to the mean of the population. On the other hand, the low-trustworthiness types form beliefs that are too conservative and thereby avoid being cheated, but give up profitable opportunities too often and, consequently, underperform. Our estimates imply that the cost of either excessive or too little trust is comparable to the income lost by foregoing college. Furthermore, we find that people who trust more are cheated more often by banks as well as when purchasing goods second hand, when relying on the services of a plumber or a mechanic and when buying food. We complement the survey evidence with experimental evidence showing that own trustworthiness and expectations of others' trustworthiness in a trust game are strongly correlated and that performance in the game is hump-shaped. |
| Keywords: | economic performance, trustworthiness, trust, culture, false consensus |
| JEL: | A1 A12 D1 O15 Z1 |
| Date: | 2009–09 |
| URL: | http://d.repec.org/n?u=RePEc:iza:izadps:dp4416&r=exp |
| By: | André De Palma (ENS Cachan - Ecole Normale Supérieure de Cachan - Ecole Normale Supérieure de Cachan, Department of Economics, Ecole Polytechnique - CNRS : UMR7176 - Polytechnique - X); Nathalie Picard (Department of Economics, Ecole Polytechnique - CNRS : UMR7176 - Polytechnique - X, THEMA - Théorie économique, modélisation et applications - CNRS : UMR8184 - Université de Cergy Pontoise); Anthony Ziegelmeyer (Max Planck Institut, Strategic Interaction Group - (-)) |
| Abstract: | This paper reports results of an experiment designed to analyze the link between risky decisions made by couples and risky decisions made separately by each spouse. We estimate both the spouses and the couples' degrees of risk aversion, we assess how the risk preferences of the two spouses aggregate when they make risky decisions and we shed light on the dynamics of the decision process that takes place when couples make risky decisions. We find that, far from being fixed, the balance of power within the household is malleable. In most couples, men have, initially, more decision-making power than women but women who ultimately implement the joint decisions gain more and more power over the course of decision making. |
| Keywords: | Balance of power; Experiments; Household decision-making; Risk. |
| Date: | 2009–09–22 |
| URL: | http://d.repec.org/n?u=RePEc:hal:wpaper:hal-00418899_v1&r=exp |
| By: | Delfgaauw, Josse (Erasmus University Rotterdam); Dur, Robert (Erasmus University Rotterdam); Sol, Joeri (Erasmus University Rotterdam); Verbeke, Willem (Erasmus University Rotterdam) |
| Abstract: | We ran a field experiment in a Dutch retail chain consisting of 128 stores. In a random sample of these stores, we introduced short-term sales competitions among subsets of stores. We find that sales competitions have a large effect on sales growth, but only in stores where the store's manager and a large fraction of the employees have the same gender. Remarkably, results are alike for sales competitions with and without monetary rewards, suggesting a high symbolic value of winning a tournament. Lastly, despite the substantial variation in team size, we find no evidence for free-riding. |
| Keywords: | sales contests, field experiment, gender differences, competition, awards |
| JEL: | C93 J16 M52 |
| Date: | 2009–09 |
| URL: | http://d.repec.org/n?u=RePEc:iza:izadps:dp4395&r=exp |
| By: | Quazi Shahriar (Department of Economics, San Diego State University) |
| Abstract: | Identity is a person’s sense of self, derived from her membership in a group. Previous experimental studies have shown that people take more favorable actions towards the members of their own group (in-group favoritism). This paper proposes a simple model of identity to capture this in-group favoritism in a private-value second-price sealed bid auction and reports the result of an experiment designed to test the predictions of the model. Consistent with the predictions, the data reveal that bids and seller revenue are higher when the seller belongs to the same group as the buyers compared to when the seller belong to a different group. |
| Date: | 2009–09 |
| URL: | http://d.repec.org/n?u=RePEc:sds:wpaper:0034&r=exp |
| By: | Hongbin Cai; Yuyu Chen; Hanming Fang; Li-An Zhou |
| Abstract: | We report results from a large randomized natural field experiment conducted in southwestern China in the context of insurance for sows. Our study sheds light on two important questions about microinsurance. First, how does access to formal insurance affect farmers' production decisions? Second, what explains the low takeup rate of formal insurance, despite substantial premium subsidy from the government? We find that providing access to formal insurance significantly increases farmers' tendency to raise sows. We argue that this finding also suggests that farmers are not previously insured efficiently through informal mechanisms. We also provide several pieces of evidence suggesting that trust, or lack thereof, for government-sponsored insurance products is a significant barrier for farmers' willingness to participate in the insurance program. |
| JEL: | C93 O12 O16 |
| Date: | 2009–10 |
| URL: | http://d.repec.org/n?u=RePEc:nbr:nberwo:15396&r=exp |
| By: | Galarza, Francisco |
| Abstract: | This paper estimates the risk preferences of cotton farmers in Southern Peru, using the results from a multiple-price-list lottery game. Assuming that preferences conform to two of the leading models of decision under risk--Expected Utility Theory (EUT) and Cumulative Prospect Theory (CPT)--there is strong evidence of moderate risk aversion. Once we include individual characteristics in the estimation of risk parameters, we observe that farmers use subjective nonlinear probability weighting, a behavior consistent with CPT. Interestingly, when we allow for preference heterogeneity via the estimation of mixture models--where the proportion of subjects who behave according to EUT or to CPT is endogenously determined--we see that the majority of farmers’ choices are best explained by CPT. We further hypothesize that the multiple switching behavior observed in our sample can be explained by nonlinear probability weighting made in a context of large random calculation mistakes; the evidence found on this regard is mixed. Finally, we find that attaining higher education is the single most important individual characteristic correlated with risk preferences, a result that suggests a connection between cognitive abilities and behavior towards risk. |
| Keywords: | risk aversion; probability weighting; mixture models; experimental economics; Peru |
| JEL: | C9 D81 |
| Date: | 2009–08 |
| URL: | http://d.repec.org/n?u=RePEc:pra:mprapa:17708&r=exp |
| By: | Fujikawa, Takemi |
| Abstract: | The ''hot stove effect'' has been studied for repeated-play decision making under uncertainty (also referred to as experience-based decision making) in which the decision makers repeatedly face the Allais-type binary choice problems, and have to learn about the outcome distributions through sampling as the decision makers are not explicitly provided with prior information on the payoff structure. The previous studies have found mixed evidence: some studies have found that the hot stove effect is strong in repeated-play decision making under uncertainty, while other studies have found that the effect is weak. Thus, the evidence is inconsistent. This paper reports an experimental investigation of the hot stove effect in repeated-play decision making under ambiguity. The current experiment involves an ambiguity treatment in which (1) the participants perform two binary repeated-play choice problems, each involving 400-fold choice between a risky option and a riskless option; and (2) in each problem, there are two states of nature available: a favourable state and an unfavourable state, but only one of them obtains on any given trial. The realisation of the actual state is not disclosed to the participants, thus they would be expected to discover the actual state through sampling with immediate feedback. The current results suggest that the magnitude of the hot stove effect is significantly different between repeated-play decision making under uncertainty and repeated-play decision making under ambiguity. I shall show that the hot stove effect is attenuated in repeated-play decision making under ambiguity. |
| Keywords: | Allais-type choices; decisions from experience; risk; uncertainty |
| JEL: | D83 C91 |
| Date: | 2009–10–03 |
| URL: | http://d.repec.org/n?u=RePEc:pra:mprapa:17647&r=exp |
| By: | Lacetera, Nicola (Case Western Reserve University); Macis, Mario (University of Michigan) |
| Abstract: | Experimental studies document that financial rewards discourage the performance of altruistic activities, because they destroy intrinsic altruistic motivations. We set up a randomized-controlled experiment, through a survey administered to 467 blood donors in an Italian town, and find that donors are not reluctant to receive compensation in general: A substantial share of respondents declared they would stop being donors if paid a small amount of cash, but we do not find such effects when a voucher of the same nominal value is offered instead. The aversion to direct cash payments is particularly marked among women and older respondents, while there are neither gender nor age differences in the response to the voucher. Implications for research and public policy are discussed. |
| Keywords: | incentives, altruism, public good provision, pro-social behavior, public health |
| JEL: | D12 D64 I18 |
| Date: | 2009–09 |
| URL: | http://d.repec.org/n?u=RePEc:iza:izadps:dp4458&r=exp |
| By: | Neil Buckley; Stuart Mestelman; R. Andrew Muller; Stephan Schott; Jingjing Zhang |
| Abstract: | Schott et al. (2007) have shown that the “tragedy of the commons” can be overcome when individuals share their output equally in groups of optimal size and there is no communication. The assignment to groups as either strangers or partners does not significantly affect this outcome. In this paper we investigate whether communication changes these results. Communication reduces shirking, increases aggregate effort and reduces aggregate rents, but only when communication and output-sharing groups are linked. The effect is stronger for fixed- membership output-sharing groups (the partner treatment) than for output-sharing groups with randomly reassigned members (the stranger treatment). Performance is not distinguishable from the no-communication treatments when communication is present but groups are sharing output within groups other than the groups within which they communicate. Communication also tends to enhance the negative effect of the partnered group assignment on the equality of individual payoffs. |
| Keywords: | Common pool resources; Communication; Coordination; Cooperation; Free-riding Behaviour in Teams; Partners and Strangers; Experiments |
| JEL: | Q20 C91 D70 C92 C71 C72 |
| Date: | 2009–10 |
| URL: | http://d.repec.org/n?u=RePEc:mcm:deptwp:2009-15&r=exp |
| By: | Buurman, Margaretha (Erasmus University Rotterdam); Dur, Robert (Erasmus University Rotterdam); van den Bossche, Seth (TNO Work and Employment) |
| Abstract: | We assess whether public sector employees have a stronger inclination to serve others and are more risk averse than employees in the private sector. A unique feature of our study is that we use revealed rather than stated preferences data. Respondents of a large-scale survey were offered a substantial reward and could choose between a widely redeemable gift certificate, a lottery ticket, or making a donation to a charity. Our analysis shows that public sector employees are significantly less likely to choose the risky option (lottery) and, at the start of their career, significantly more likely to choose the pro-social option (charity). However, when tenure increases, this difference in pro-social inclinations disappears and, later on, even reverses. Our results further suggest that quite a few public sector employees do not contribute to charity because they feel that they already contribute enough to society at work for too little pay. |
| Keywords: | public service motivation, risk aversion, revealed preferences data |
| JEL: | H1 J45 M52 |
| Date: | 2009–09 |
| URL: | http://d.repec.org/n?u=RePEc:iza:izadps:dp4401&r=exp |
| By: | Kiridaran Kanagaretnam; Stuart Mestelman; Khalid Nainar; Mohamed Shehata |
| Abstract: | This paper uses laboratory mechanism design in an investment environment to examine the impact of empowering investors with the right to veto the investee’s profit distribution decision on the level of trust and trustworthiness. One of the key findings is that the empowerment of investors through both costless and costly vetoes significantly increases trust by over 30% in both cases. Interestingly, we observe a comparable pattern when the power to veto is removed. Analyses of veto decisions indicate that empowering investors increases both trust and trustworthiness without an undue abuse of the power to veto and that the veto decisions are largely driven by unfair responses, consistent with the theory on inequity aversion. |
| Keywords: | Empowerment; Veto; Investment; Trust; Trustworthiness; Reciprocity |
| JEL: | C70 C91 D63 D81 D82 |
| Date: | 2009–09 |
| URL: | http://d.repec.org/n?u=RePEc:mcm:deptwp:2009-16=&r=exp |
| By: | Comerford, David (University College Dublin); Delaney, Liam (University College Dublin); Harmon, Colm P. (University College Dublin) |
| Abstract: | This paper tests for a number of survey effects in the elicitation of expenditure items. In particular we examine the extent to which individuals use features of the expenditure question to construct their answers. We test whether respondents interpret question wording as researchers intend and examine the extent to which prompts, clarifications and seemingly arbitrary features of survey design influence expenditure reports. We find that over one quarter of respondents have difficulty distinguishing between "you" and “your household” when making expenditure reports; that respondents report higher pro-rata expenditure when asked to give responses on a weekly as opposed to monthly or annual time scale; that respondents give higher estimates when using a scale with a higher mid-point; and that respondents report higher aggregated expenditure when categories are presented in a disaggregated form. In summary, expenditure reports are constructed using convenient rules of thumb and available information, which will depend on the characteristics of the respondent, the expenditure domain and features of the survey question. It is crucial to further account for these features in ongoing surveys. |
| Keywords: | expenditure surveys, survey design, data experiments |
| JEL: | D12 C81 C93 |
| Date: | 2009–09 |
| URL: | http://d.repec.org/n?u=RePEc:iza:izadps:dp4389&r=exp |
| By: | Migheli, Matteo |
| Abstract: | This paper studies how individual religiosity affects people's behaviour. In particular here I study the behaviour of the second players in a standard trust game. They have the possibility of sharing some resources between themselves and their game mates. It results that more religious people tend to choose an even allocation of these resources, whilst the less religious participants are either opportunistic or generous. |
| Keywords: | religiosity, distribution of resources, inequity aversion |
| JEL: | C93 D30 Z12 |
| Date: | 2009–09 |
| URL: | http://d.repec.org/n?u=RePEc:uca:ucapdv:133&r=exp |
| By: | Flores, Carlos A. (University of Miami); Mitnik, Oscar A. (University of Miami) |
| Abstract: | This paper assesses the effectiveness of unconfoundedness-based estimators of mean effects for multiple or multivalued treatments in eliminating biases arising from nonrandom treatment assignment. We evaluate these multiple treatment estimators by simultaneously equalizing average outcomes among several control groups from a randomized experiment. We study linear regression estimators as well as partial mean and weighting estimators based on the generalized propensity score (GPS). We also study the use of the GPS in assessing the comparability of individuals among the different treatment groups, and propose a strategy to determine the overlap or common support region that is less stringent than those previously used in the literature. Our results show that in the multiple treatment setting there may be treatment groups for which it is extremely difficult to find valid comparison groups, and that the GPS plays a significant role in identifying those groups. In such situations, the estimators we consider perform poorly. However, their performance improves considerably once attention is restricted to those treatment groups with adequate overlap quality, with difference-in-difference estimators performing the best. Our results suggest that unconfoundedness-based estimators are a valuable econometric tool for evaluating multiple treatments, as long as the overlap quality is satisfactory. |
| Keywords: | multiple treatments, nonexperimental estimators, generalized propensity score |
| JEL: | C13 C14 C21 |
| Date: | 2009–09 |
| URL: | http://d.repec.org/n?u=RePEc:iza:izadps:dp4451&r=exp |
| By: | Ernst Fehr (University of Zurich); Klaus M. Schmidt (University of Munich) |
| Abstract: | In this paper we reply to Binmore and Shaked’s criticism of the Fehr-Schmidt model of inequity aversion. We put the theory and their arguments into perspective and show that their criticism is not substantiated. Finally, we briefly comment on the main challenges for future research on social preferences |
| Keywords: | Experiments, other-regarding preferences, inequity aversion |
| JEL: | B41 C90 |
| Date: | 2009–02 |
| URL: | http://d.repec.org/n?u=RePEc:trf:wpaper:276&r=exp |
| By: | Ahmed Doghmi (Strategic Interaction Group, Max Planck Institute of Economics, Jena, Germany); Miloudi Kobiyh (Center for Research in Economics and Management, University of Caen, France) |
| Abstract: | In this paper, we introduce the concept of payoffi distortion in the standard prisoner's dilemma game when strategies are driven by psychological behaviors. This concept enables to take account each player's assessment of the other player's behavior and the asymmetry of information. We determine the conditions which allow that mutual cooperation constitutes the equilibrium. we particularly focus on the reciprocity in case of complete and incomplete information about the payoffi distortion. We show that mutual cooperation is a Nash equilibrium with complete information and is a Bayesian equilibrium when each player believes that his opponent behaves with "large" reciprocity in incomplete information environment. |
| Keywords: | Reciprocity, Behavior, Cooperation, prisoner's dilemma game. |
| JEL: | C7 A13 |
| Date: | 2009–09–25 |
| URL: | http://d.repec.org/n?u=RePEc:jrp:jrpwrp:2009-072&r=exp |
| By: | De Giorgi, Giacomo (Stanford University); Pellizzari, Michele (Bocconi University); Woolston, William Gui (Stanford University) |
| Abstract: | We study how class size and composition affect the academic and labor market performances of college students, two crucial policy questions given the secular increase in college enrollment. We rely on the random assignment of students to teaching classes. Our results suggest that a one standard deviation increase in the class-size would result in a 0.1 standard deviation deterioration of the average grade. Further, the effect is heterogenous as female and higher income students seem almost immune to the size of the class. Also, the effects on performance of class composition in terms of gender and ability appears to be inverse U-shaped. Finally, a reduction of 20 students (one standard deviation) in one's class size has a positive effect on monthly wages of about 80 Euros (115 USD) or 6% over the average. |
| Keywords: | class size, heterogeneity, experimental evidence, academic performance, wages |
| JEL: | A22 I23 J30 |
| Date: | 2009–09 |
| URL: | http://d.repec.org/n?u=RePEc:iza:izadps:dp4443&r=exp |
| By: | Meliyanni Johar (CHERE, University of Technology, Sydney); Denzil Fiebig; Marion Haas (CHERE, University of Technology, Sydney); Rosalie Viney (CHERE, University of Technology, Sydney) |
| Abstract: | This study examines behavioural changes brought about by two interventions introduced to lower the incidence of cervical cancer in Australia. The first intervention is a media campaign promoting regular screening behaviour to women. The second intervention is a vaccination program providing a free HPV vaccine, Gardasil, to young women launched in the same period. The results using data from discrete choice experiments find that in general, given individual characteristics, the interventions have minor impact on how women value screening attributes. The interventions however alter womenís inherent taste for screening. Unexpectedly, willingness to screen is generally lower post-interventions. The reason for this trend appears to be related to HPV events. For instance, the reduction in screening participation is particularly marked among young women who are eligible for the vaccination program. There is also a larger aversion towards testing among women who gained information on HPV facts and HPV-related measures. Thus, in the face of HPV innovations, screening promotions need to account for these factors. A simulation exercise is then performed to assess the plausibility of several strategies to increase the screening rate. The results nominate supply-side policies, in particular those targeted to health providers, as the most effective strategy. |
| Keywords: | cervical screening, HPV Vaccine, preferences, discrete choice experiment, Australia |
| JEL: | I10 |
| Date: | 2009–06 |
| URL: | http://d.repec.org/n?u=RePEc:her:chewps:2009/3&r=exp |