Using data from over 100 US retirement plans and a representative UK panel, I document the impact of auto-enrollment (AE) on retirement savings at different horizons. I replicate the impact of AE on participation and contributions in the short run (at 12 months), but I show that these gains are attenuated over the medium run (at 36 months). At this longer horizon, the average savings increases are modest, though AE significantly lowers inequality in savings. To assess AE’s lifetime impact, I estimate a life cycle consumption-savings model that can fit the observed patterns with a switching cost of approximately $250, smaller than previous estimates. (JEL D15, G51, J26, J32)

ABSTRACT We study the role of risk preferences and frictions in portfolio choice using variation in 401(k) default options. Patterns of active choice in response to different default funds imply that, absent participation frictions, 94% of investors prefer holding stocks, with an equity share of retirement wealth declining with age—patterns markedly different from observed allocations. We use this quasi‐experiment to estimate a life‐cycle model and find a relative risk aversion of 2.5, elasticity of intertemporal substitution (EIS) of 0.25, and $160 portfolio adjustment cost. The results suggest that low levels of stock market participation in retirement accounts are due to participation frictions rather than nonstandard preferences such as loss aversion.

We study how couples allocate retirement-saving contributions across each spouse’s account. In a new dataset covering over a million US individuals, we find retirement contributions are not allocated to the account with the highest employer match rate. This lack of coordination—which goes against the assumptions of most models of household decision-making—is common, costly, persistent over time, and cannot be explained by inertia, auto-enrollment, or simple heuristics. Complementing the administrative evidence with an online survey, we find that inefficient allocations reflect both financial mistakes as well as deliberate choices, especially when trust and commitment inside the households are weak. (JEL D13, G51, J26, J32)