Model summary
The approach adopted in this study utilized two equations – a binary model for whether an individual
under-reports or not and an ordered-response model for the number of trips under-reported if there is
under-reporting at all. The methodology it accounts for the correlation in error terms between the two
equations. That is, it accounts for the potential presence of unobserved individual factors (such as, say, an
overall disinclination to respond to surveys or substantial time constraints) that influences both whether
an individual under-reports as well as the level of under-reporting. For a more detailed discussion of the
modeling portion of this research, see Bricka and Bhat (2005).
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