A comparison between willingness to pay and willingness to give up time
We compared the willingness-to-pay and willingness to give up time methods to assess preferences for digital subtraction angiography (DSA), computed tomography angiography (CTA) and magnetic resonance angiography (MRA). Respondents were hypertensive patients suspected of having renal artery stenosis. Data were gathered using telephone interviews. Both the willingness-to-pay and willingness to give up time methods revealed that patients preferred CTA to MRA in order to avoid DSA. The agreement between willingness-to-pay and willingness to give up time responses was high (kappa 0.65-0.85). The willingness-to-pay method yielded relatively more protest answers (12%) as compared to willingness to give up time (2%). So, our results provided evidence for the comparability of willingness to pay and willingness to give up time. The high percentage of protest answers on the willingness-to-pay questions raises questions with respect to the application of the willingness-to-pay method in a broad decision-making context. On the other hand, the strength of willingness-to-pay is that the method directly arrives at a monetary measure well founded in economic theory, whereas the willingness to give up time method requires conversion to monetary units.