History: Sunk Cost, or Widespread Externality?

In an intertemporal Arrow-Debreu economy with a continuum of agents, suppose that the auctioneer sets prices while the government institutes optimal lump-sum transfers period by period. An earlier paper showed how subgame imperfections arise because agents understand how their current decisions such as those determining investment will influence future lump-sum transfers. This observation undermines the second efficiency theorem of welfare economics and makes «history» a widespread externality. A two-period model is used to investigate the constrained efficiency properties of different kinds of equilibrium. Possibilities for remedial policy are also discussed.