  In the problem of allocating a single non-disposable commodity among agents
whose preferences are single-peaked, we study a weakening of strategy-proofness
called not obvious manipulability (NOM). If agents are cognitively limited,
then NOM is sufficient to describe their strategic behavior. We characterize a
large family of own-peak-only rules that satisfy efficiency, NOM, and a minimal
fairness condition. We call these rules "simple". In economies with excess
demand, simple rules fully satiate agents whose peak amount is less than or
equal to equal division and assign, to each remaining agent, an amount between
equal division and his peak. In economies with excess supply, simple rules are
defined symmetrically. These rules can be thought of as a two-step procedure
that involves solving a claims problem. We also show that the single-plateaued
domain is maximal for the characterizing properties of simple rules. Therefore,
even though replacing strategy-proofness with NOM greatly expands the family of
admissible rules, the maximal domain of preferences involved remains basically
unaltered.
