Who answers 'willingness to pay' questions?

The objectives of this study were twofold. The first was to compare characteristics of responders and non-responders to a survey of women attending a bone mineral density screening service in Aberdeen concerned with the screening process which contained questions on attenders' willingness to pay (WTP) and willingness to wait (WTW) for screening. The second objective was to compare the characteristics of those responding to either the WTP or the WTW questions relative to those who responded to both.

After receiving a scan, women completed the questionnaire at the clinic or returned it by post. Logistic regression analysis was used to compare the characteristics of the responders and non-responders.

Those who smoked were less likely to return the questionnaire, whilst those who drank alcohol were more likely to return it. The majority of respondents answered both WTP and WTW questions. The proportions responding to the WTW and WTP questions were 93.2% and 81.5% for the two questions, respectively (95% confidence interval of difference = 9.4% to 13.9%). The only result which was statistically significant at the 1% level showed that, relative to those who answered the WTW but not the WTP questions, those who answered both were more likely to be older when they left full-time education. A weaker statistical association (at the 5% level) revealed that those who were older when leaving full-time education were more likely to answer a WTP question than not.

WTP questions seem to be less acceptable to those who leave full-time education earlier. Analysts may need to account for this in future studies. Whether such results can be replicated and reasons for non-response should be investigated.