On Existence, Efficiency and Bubbles of Ramsey Equilibrium with Borrowing Constraints

We address the fundamental issues of existence and efficiency of a Ramsey equilibrium with heterogenous discounting, elastic labor supply and borrowing constraints. In the first part, we prove the equilibrium existence in a truncated bounded economy through a fixed-point argument by Gale and Mas-Colell (1975). This equilibrium is also an equilibrium of any unbounded economy with the same fundamentals. The proof of existence is eventually given for an infinite-horizon economy as a limit of a sequence of truncated economies. Our general approach is suitable for applications to other models with different market imperfections. In the second part, we show the impossibility of bubbles in a productive economy and we give sufficient conditions for equilibrium efficiency.