  Finding the optimal policy for multi-period perishable inventory systems
requires solving computationally-expensive stochastic dynamic programs (DP). To
avoid the difficulty of solving DP models, we propose a framework that uses an
externality term to capture the long-term impact of ordering decisions on the
average cost over an infinite horizon. By approximating the externality term,
we yield a tractable approximate optimality condition, which is solved through
standard marginal analysis. The resulted policy is near-optimal in long-run
average cost and ordering decisions.
