Most evaluation of Health Impact Assessments uses the terms: process, impact and outcome, which are explained below.
Process evaluation involves collecting information on the procedures for undertaking the HIA, who was involved, what resources were used. The case study guide (see below) should be used to ensure consistent and comparable case studies are produced. All costs of an HIA should be recorded as accurately as possible, as is suggested in the case study guide. This information could also be used for future cost utility or costs benefit analyses.
Impact evaluation considers the things that might change as a result of the HIA, and how effective the HIA was in meeting its aims and objectives. Case studies should include some indication of whether decision makers perceived the HIA as adding value, and of whether health impacts were considered by decision makers. Monitoring of whether recommendations were adopted should also always be undertaken. HIA impact evaluation should include consideration of indirect impacts important in the New Zealand context; such as developing relationships between stakeholders and policy makers, and an increased recognition of the importance of health.
Outcome evaluation measures the long-term effects of an HIA. Outcome evaluation may not be a priority for HIA evaluation because it is resource intensive and causal associations are difficult to demonstrate. Collecting information on a range of indicators of health and wellbeing and their determinants, including their distribution in the population, both before the policy is implemented and on an ongoing basis following policy implementation is none the less important. Such data can be used to inform HIA; to assess the accuracy of HIA predictions; and to monitor the health impacts of the HIA and the policy it assessed. HIA practitioners should work with those commissioning the HIA to establish appropriate data sources and indicators for HIA.
Formative evaluation is less frequently referred to in the HIA literature, but is also an important part of evaluation activity. Formative evaluation involves gathering information in order to plan, refine and improve the HIA, and is generally undertaken internally by the project team. It is often not published, so there are no examples of formative HIA evaluation to draw on. Guidance on undertaking HIA, such as the PHAC and the Whanau Ora HIA tools, can be important tools for the formative evaluation of an HIA. Health promotion evaluation guidance is also helpful.