An overlapping generations model of social security with productivity and demographic shocks is studied. The authors focus attention on stationary long-run allocations. An allocation is interim optimal if there does not exist another feasible allocation that improves the expected welfare of all...

A set of n objects and an amount M of money is to be distributed among m people. Example: the objects are tasks and the money is compensation from a fixed budget. An elementary argument via constrained optimization shows that for M sufficiently large the set of efficient, envy free allocations...

An effectivity function describes the blocking power of coalitions on subsets of alternatives. Given a preference profile, if any coalition blocks an alternative whenever it can, using its own power and making all of its members better off, only alternatives in the core can be reached. In this...