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dc.contributor.authorStewart, Jayen_US
dc.date.accessioned2010-01-22en_US
dc.date.accessioned2010-07-07T12:04:24Z-
dc.date.available2010-07-07T12:04:24Z-
dc.date.issued2009en_US
dc.identifier.urihttp://hdl.handle.net/10419/35935-
dc.description.abstractTime-use surveys collect very detailed information about individuals' activities over a short period of time, typically one day. As a result, a large fraction of observations have values of zero for the time spent in many activities, even for individuals who do the activity on a regular basis. For example, it is safe to assume that all parents do at least some childcare, but a relatively large fraction report no time spent in childcare on their diary day. Because of the large number of zeros Tobit would seem to be the natural approach. However, it is important to recognize that the zeros in time-use data arise from a mismatch between the reference period of the data (the diary day) and the period of interest, which is typically much longer. Thus it is not clear that Tobit is appropriate. In this study, I examine the bias associated with alternative estimation procedures for estimating the marginal effects of covariates on time use. I begin by adapting the infrequency of purchase model, which is typically used to analyze expenditures, to time-diary data and showing that OLS estimates are unbiased. Next, using simulated data, I examine the bias associated with three procedures that are commonly used to analyze time-diary data - Tobit, the Cragg (1971) two-part model, and OLS - under a number of alternative assumptions about the data-generating process. I find that the estimated marginal effects from Tobits are biased and that the extent of the bias varies with the fraction of zero-value observations. The two-part model performs significantly better, but generates biased estimated in certain circumstances. Only OLS generates unbiased estimates in all of the simulations considered here.en_US
dc.language.isoengen_US
dc.publisherIZA Bonnen_US
dc.relation.ispartofseriesIZA Discussion Papers 4588en_US
dc.subject.jelC24en_US
dc.subject.jelJ22en_US
dc.subject.ddc330en_US
dc.subject.keywordTobiten_US
dc.subject.keywordtime useen_US
dc.subject.stwZeitbudgetforschungen_US
dc.subject.stwTobit-Modellen_US
dc.titleTobit or not tobit?en_US
dc.typeWorking Paperen_US
dc.identifier.ppn617000522en_US
dc.rightshttp://www.econstor.eu/dspace/Nutzungsbedingungen-
Appears in Collections:IZA Discussion Papers, Forschungsinstitut zur Zukunft der Arbeit (IZA)

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