It is often observed that WTP for a health risk reduction does not sensitively react
to the extent of risk reduction. This is of concern when valuing policy scenarios. It is
found that the WTP evaluated in a holisitic scenario is smaller than the sum of WTP
for a partition of decomposed scenarios (Hammerschmidt et al. 2004). In the context
of health technology evaluation, Hammerschmidt et al. (2004) came to the
conclusion that sub-additivity can result because of effects of health on the marginal
utility of wealth. However, Hammitt and Graham (1999) suggest that for small
changes in health risks WTP should be approximately proportional to probabilities.
On the other hand, Randall and Hoehn (1996) denote embedding to be an ordinary
economic phenomenon.