Behavioural messages amplify tax incentives: A nationwide megastudy of retirement savings reminders

Insufficient retirement savings threaten financial security worldwide as individuals increasingly bear responsibility for funding their retirement. We present the first population-level test of behaviourally informed messaging for boosting saving in retirement accounts. In collaboration with the Estonian Ministry of Finance, we conducted a preregistered randomized controlled trial among all eligible account holders (N = 127,974) testing whether email reminders about tax benefits boost voluntary pension contributions. Across nine behaviourally designed reminders versus a no-reminder control, reminders increased contribution likelihood by 10.49% and raised average contributions by 14.75% within one week before the deadline. Most framings increased participation but notably, a family-security message also increased individual contribution size (from €868 to €1,009). Exploratory causal forest analysis revealed the baseline message most strongly influenced younger, higher-income individuals with prior contributions, while the family-security message had the largest impact on high-income individuals. The intervention generated ~€1.2 million in additional retirement savings within one week. These results show that simple, low-cost behavioural reminders can meaningfully amplify tax incentives at scale, offering practical tools for policymakers.