Mandatory retirement savings in the presence of an informal labor market
研究发现，强制工人增加退休储蓄可能导致他们转向非正规工作并减少储蓄；降低缴费率反而可能增加退休储蓄，因为非正规工作相当于对强制储蓄的借贷，缴费率降低会提高这种借贷的成本，促使工人回归正规部门。
Abstract This paper shows how mandating workers to save more for retirement can lead them to work informally and save less. Consider a worker who is more productive in the formal sector but works informally to avoid mandatory retirement contributions. Lowering the contribution rate (the share of wages mandated to be saved) will paradoxically increase her retirement savings. The reason for this is that working informally acts as borrowing against mandatory savings. The implicit cost of such borrowing, and hence the opportunity cost of working informally, rises as the contribution rate drops. This creates a substitution effect favoring formal work, driving the worker towards the formal sector. As her formal income increases, the base for her mandatory contributions rises, expanding her retirement savings. Therefore, the optimal contribution rate is no greater than the highest contribution rate under which the worker prefers to work exclusively in the formal sector.