Assessing Nudge Impact: A Comprehensive Second‐Order Meta‐Analysis

Nudging as a strategy to alter behaviors has garnered increasing attention from both researchers and policymakers. Here, we conduct a second‐order meta‐analysis, synthesizing 13 articles (14 meta‐analyses) that include 1638 primary studies and approximately 30 million participants. We find a small aggregated effect size across these meta‐analyses ( d = 0.27, 95% CI [0.16, 0.38]), which drops to d = 0.004 after adjusting for publication bias. Examining the methodological quality of the meta‐analyses, we find that most were rated as low or critically low, suggesting that our findings, which inherit these limitations, should be interpreted with caution. This study provides the most comprehensive synthesis of the effectiveness of nudging to date, while underscoring the urgent need for higher quality, preregistered meta‐analyses to clarify the true impact.