Financial ServicesDefaultPositive

401(k) Auto-Enrollment and Save More Tomorrow

University of Chicago / University of California Berkeley · Multiple US companies · 1998

Summary

The auto-enrollment and Save More Tomorrow experiments are the most consequential applications of behavioral economics to public policy. The insight is simple but powerful: retirement savings rates are not determined by workers' conscious preferences but by the default option they face. When enrollment requires action (opt-in), inertia keeps workers out. When non-enrollment requires action (opt-out), inertia keeps workers in. Switching the default from opt-in to opt-out raised participation from 49% to 86% — a 37-percentage-point change achieved by reframing inaction. SMarT extended the insight: workers who won't save now will commit to saving future raises they haven't received yet, because the loss feels abstract. The experiments proved that default design is retirement policy, not just administrative procedure, and triggered a legislative revolution in US retirement savings architecture.

Research question

"Can default enrollment in retirement savings plans — and pre-commitment to future savings increases — dramatically raise retirement savings participation and contribution rates among workers?"

Methodology

Intervention

Two complementary experiments: (1) Madrian & Shea (2001): A large US corporation switched its 401(k) plan from opt-in (workers must actively enroll) to auto-enrollment with a default 3% contribution. Existing employees were unaffected; only new hires were auto-enrolled. (2) Thaler & Benartzi (2004): The Save More Tomorrow (SMarT) program offered workers the option to pre-commit future salary raises to retirement savings. Workers who agreed would have a portion of each future raise automatically redirected to their 401(k) before they received it in their paycheck.

Assignment

(1) Natural experiment: Madrian & Shea compared participation rates before and after policy change, with before-cohort as control. (2) SMarT program: offered to workers who declined to increase contributions when asked; those who signed up were compared to those who declined, with analysis of pre-commitment effects

Sample size

(1) Approximately 3,000 new hires across two cohorts (pre- and post-auto-enrollment). (2) SMarT program: 315 workers at a manufacturing company offered the program

Primary outcome

Retirement plan participation rate; contribution rate (% of salary saved)

Effect estimate

(1) Auto-enrollment: participation rate jumped from 49% to 86% within 3 months of hire; at 3–15 months, 86% of auto-enrolled workers still enrolled (vs. 65% who would have actively opted in). (2) SMarT: workers who joined pre-committed their savings rate from 3.5% to 13.6% over four plan-raise cycles — nearly quadrupling their savings rate vs. those who declined.

Decision

The Pension Protection Act of 2006 encouraged auto-enrollment nationwide; auto-enrollment is now standard in large US employer plans; approximately 80% of large-company plans use auto-enrollment as of 2020; the 2022 SECURE 2.0 Act mandated auto-enrollment for new employer plans; Save More Tomorrow has been adopted by hundreds of companies and is estimated to have raised savings rates for millions of American workers; auto-enrollment has become the canonical example of 'libertarian paternalism' — preserving choice while using defaults to improve welfare-enhancing behavior

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Result

Positive

Evidence strength

Limited

Observational or pre-post design; correlation not necessarily causal.

Replication status

Replicated

Institution

University of Chicago / University of California Berkeley

Location

Multiple US companies

Year

1998

Policy area

Financial Services

Mechanism

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