MIT economist Jonathan Gruber lectures on how the tax code shapes retirement saving, part of his Public Finance and Public Policy course (14.41, Fall 2024). He walks through the four main vehicles adults use to save for retirement: employer pensions, 401(k) accounts, IRAs, and SEP-IRAs, comparing how each is taxed and subsidized. Gruber works through the economic logic of why the government subsidizes saving at all, what these incentives cost in forgone revenue, and the empirical evidence on whether tax breaks actually increase net saving or simply shift where existing savings are held. The lecture builds on standard public finance tools, applying them to a concrete policy question that touches nearly every American worker's paycheck. Delivered in Gruber's usual direct, blackboard-and-slides style, it is aimed at students who have already covered the course's earlier material on taxation and behavior.