The Perception-Adjusted Luce Model (PALM) introduced by by Echenique et al. (2018) is a sequential choice model that can accommodate violations of regularity and choice overload, behaviors not captured by the utility-maximization framework. Flores et al. (2019) studied the assortment problem under the PALM and proved that, for the case of two levels, there is always an optimal solution that is revenue-ordered by level. They also conjectured that revenue-ordered by levels remain optimal for the general PALM with any number of levels. We resolve this question in the affirmative by showing that every PALM instance admits an optimal assortment that includes, within each level, all products at or above a level-specific revenue threshold. The proof involves first showing how the conjecture which deals with a discrete optimization problem, can be reduced to proving certain property of a related continuous optimization problem. Specifically, we study a continuous refinement of the assortment decision under the same PALM choice rule. Although the refinement permits partial utility selections, we prove it always has an optimum that selects complete revenue tiers. This allows us to show that the assortment problem is polynomial-time solvable when the number of levels is fixed.

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