Soft data, hard effects. Strategies for effective policy on health impact assessment--an example from the Netherlands.

Health impact assessment (HIA) on a strategic level focuses on the broad determinants of health. However, the evidence with regard to the health impacts is often necessarily 'soft'. The example of a health impact review on national housing policy in the Netherlands shows that HIA can be effective even in the absence of hard data. Strategies used to overcome the problem of not having hard data are outlined. The authors argue that, for HIA to be effective, it does not necessarily have to be limited to easy-to-measure, easy-to-quantify programmes and health effects.