On Adding-Up as a Validity Criterion for Stated-Preference Studies

The adding-up test, which requires that the value of a bundle of goods or services be equal to the sum of the values of its component parts, has been proposed as a validity criterion for stated-preference studies. Though rooted in accepted theory, this proposal raises practical issues that need to be resolved before it is ready for implementation. It requires assumptions about preferences beyond those required for other validity tests such as the scope test. Surveys to implement adding up also increase respondent burden and may compromise consequentiality. These and other issues are reviewed and research strategies to address them are considered.