A good way to boost sales? Effects of the proportion of sold-out options on purchase behavior

The present research explores how the proportion of sold-out options in the choice set affects consumer purchase choices. Across five experiments, we find an inverted U-shaped relationship between the proportion of sold-out options in a choice set and consumer purchase choices. Fueling this effect are two competing processes: presence of sold-out options signals the overall quality of products in the choice set, which prompts consumers to purchase available options; while it also evokes psychological reactance, which impedes purchases. The quality signaling effect features a concave shape, whereas the psychological reactance force takes on a convex shape, so in combination, these two forces form an inverted U-shaped relationship. In addition, two boundary conditions were identified: (1) this effect is obtained only when psychological reactance is not induced by other situational factors; and (2) this effect disappears when consumers make purchases for others, not when they make purchases for themselves.