We study the socially optimal level of illiquidity in an economy populated by households with taste shocks and present bias with naive beliefs. The government chooses mandatory contributions to accounts, each with a different pre-retirement withdrawal penalty. Collected penalties are rebated lump sum. When households have homogeneous present bias, β, the social optimum is well approximated by a single account with an early-withdrawal penalty of 1−β. When households have heterogeneous present bias, the social optimum is well approximated by a two-account system: (i) an account that is completely liquid and (ii) an account that is completely illiquid until retirement.

Does automatic enrollment into a retirement plan increase financial distress due to increased borrowing outside the plan? We study a natural experiment created when the U.S. Army began automatically enrolling newly hired civilian employees into the Thrift Savings Plan. Four years after hire, automatic enrollmentincreases cumulative contributions to the plan by 4.1% of annual salary, but we find little evidence ofincreased financial distress. Automatic enrollment causes no significant change in credit scores, debt balances excluding auto debt and first mortgages, or adverse credit outcomes, with the possible exception of increasedfirst‐mortgage balances in foreclosure.