1016 Journal of Economic Literature,Vol.XLII (December 2004 separability),impose structure on technology could be applied to real people,but to actu- and preferences (e.g.,constant returns to ally do so entails some serious and often scale or unitary income elasticities).and sim unattractive logistical problems. plifying assumptions about equilibrium out- A more substantial response to this criti- comes (e.g.,zero-profit conditions defining cism is to consider what it is about students equilibrium industrial structure).Perhaps the that is viewed.a priori.as being nonrepre best-known class of such structural models is sentative of the target population.There are putable general equilibrium models. at least two issues here.The first is whether which have been extensively a endogenous sample selection or attrition has ate trade policies,for example ncourred due to incom lete control ove relies on c estimation strategi so that the eters that mple is sta simulatio sen e.g. onsistent sitivity analys trea al mode n this s se ether can be inform een the c ative on the behav or the population, experimenta tax and assuming away sample selection issues. policies (R.Blun ll and Thomas MaCurdy 4.2 Sample Selection in the Field 1999:and Blundell and M.Costas Dias 2002) Conventional lab experiments typically 4.Artefactual Field Experiments use students who are recruited after being told only general statements about the 4.1 The Nature of the Subject Pool experiment.By and large.recruitment pro A common criticism of the relevance of cedures avoid mentioning the nature of the inferences drawn from laboratory experi- task,or the expected earnings.Most lab ments is that one needs to undertake an xperiments are also one-shot.in the experiment with"real"people,not students that they do ot involve ated obse This criticism is often deflected by experi of a mpl ect to menters with the following imperative:if you eith ed to of the think that the experiment will generate differ If one w with spec ent results with"real"p ople,then go ahead rest i a task ould be o do and run the expe le.A (e.g.,Peter m and Han ind 1993).An ant of this is to challer the if one wanted to recruit subjects for several ics'asse tudents ses super-expenenced or to conduct pre-tests of such trust.or other an things as risk aversion st response,to suggest regarding preferences that could be built the experiment with real people into the design as well often adequate to get rid of unwanted refer One concern with lab experiments con ees at academic journals.In practice.howev ducted with convenience san oles of students er,few experimenters ever examine fielo behavior in a serious and large-sample way It is relatively easy to say that the experiment onard reen (19)for dramati theory to organ For example.the Pl king and David Tarr (197 or exampe John Kagel and Dan Levin( Harrison and H.D.Vinod (1992)