This study examined the effectiveness of health impact assessments (HIAs) conducted in Australia and New Zealand between 2005 and 2009. The researchers identified 55 HIAs and surveyed those involved to assess the level of effectiveness. They also conducted 11 in-depth case studies. The study found that 89% of HIAs were directly or generally effective in changing decisions, with factors like support from decision-makers, community engagement, and timely involvement increasing effectiveness. While no single factor guarantees success, the study demonstrates that HIAs can be an effective tool to incorporate health considerations into public policy decisions.