Effects of ES knowledge attributes on policy impact. Bars depict mean (±SE) levels of impact based on five-point expert assessment. For each attribute of knowledge (i.e., salience, credibility, and legitimacy), the 15 cases are divided into low, medium, and high categories for comparison, based on survey scores. No SE bar indicates one case in that category. **P < 0.01; *P < 0.05; +P < 0.1.