Variables used in the random-effects model to explain the heterogeneity in the WTP estimate for vehicle sharing.

<p>Variables used in the random-effects model to explain the heterogeneity in the WTP estimate for vehicle sharing.</p

Do labeled versus unlabeled treatments of alternatives’ names influence stated choice outputs? Results from a mode choice study

<div><p>Discrete choice experiments have been widely applied to elicit behavioral preferences in the literature. In many of these experiments, the alternatives are <i>named alternatives</i>, meaning that they are naturally associated with specific names. For example, in a mode choice study, the alternatives can be associated with names such as car, taxi, bus, and subway. A fundamental issue that arises in stated choice experiments is whether to treat the alternatives’ names as labels (that is, labeled treatment), or as attributes (that is, unlabeled treatment) in the design as well as the presentation phases of the choice sets. In this research, we investigate the impact of labeled versus unlabeled treatments of alternatives’ names on the outcome of stated choice experiments, a question that has not been thoroughly investigated in the literature. Using results from a mode choice study, we find that the labeled or the unlabeled treatment of alternatives’ names in either the design or the presentation phase of the choice experiment does not statistically affect the estimates of the coefficient parameters. We then proceed to measure the influence toward the willingness-to-pay (WTP) estimates. By using a random-effects model to relate the conditional WTP estimates to the socioeconomic characteristics of the individuals and the labeled versus unlabeled treatments of alternatives’ names, we find that: a) Given the treatment of alternatives’ names in the presentation phase, the treatment of alternatives’ names in the design phase does not statistically affect the estimates of the WTP measures; and b) Given the treatment of alternatives’ names in the design phase, the labeled treatment of alternatives’ names in the presentation phase causes the corresponding WTP estimates to be slightly higher.</p></div

The attributes and their levels in our mode choice study.

<p>The attributes and their levels in our mode choice study.</p

Detailed steps for the likelihood ratio tests.

<p>Detailed steps for the likelihood ratio tests.</p

The labeled versus unlabeled treatments of alternatives’ names in the design and the presentation phases produce four types of questions for a choice experiment.

<p>The labeled versus unlabeled treatments of alternatives’ names in the design and the presentation phases produce four types of questions for a choice experiment.</p

If we allow the alternatives’ names to be removed, altogether five types of questions involving named alternatives can be produced.

<p>If we allow the alternatives’ names to be removed, altogether five types of questions involving named alternatives can be produced.</p

The hypothesis tests we conduct on the four data sets.

<p>The results are summarized into Findings 1 and 2 in the text.</p

Estimation results for the mixed logit models.

<p>Estimation results for the mixed logit models.</p

Parameter estimates for the random-effects model.

<p>Parameter estimates for the random-effects model.</p

An example for the unlabeled treatment of alternatives’ names in the presentation phase.

<p>The names (that is, car, bus, and subway) are displayed in the row that corresponds to “travel mode”.</p