Getting to the root causes of 401(k) leakage is essential if U.S. workers are going to enjoy a secure retirement, experts told a Senate committee. Most 401(k) withdrawals are used to avoid circumstances such as foreclosure, but cash-outs and permanent withdrawals are far more damaging to retirement security, said Alison Borland of Aon Hewitt. A lack of other savings, such as for college and emergencies, also puts many Americans at risk for an underfunded retirement and is prompting more employers to discuss financial wellness, experts said.