This paper studies the design of an optimal pension scheme in an OLG and open economy model. The pension scheme provides a flat rate benefit and is based on the PAYG principle. It thus combines inter- and intra-generational redistribution. In this setting a number of symmetric economies are connected by an open and perfect capital market. When this number is very large, we have the small open economy case; when it is reduced to one, we have the case of autarky or perfect coordination. As the number of countries increases, there is more intragenerational redistribution, but less capital accumulation