Abstract:

Current research has shown that numbers impact consumer decision-making. The number “zero”, owing to its features as being the minimum natural number and non-divider, influences consumer decision-making through its combinations with the price and attribute dimensions of products. Scholars refer to the effects of zero price and zero attribute on consumption decision-making as the zero-price effect and the zero-comparison effect, respectively. The zero-price effect refers to the phenomenon that in the selection between high- and low-price products, when all product prices are reduced by the same amount and the price of the low-priced product is reduced to zero, the proportion of high-priced product being selected decreases and the proportion of low-priced (free) product being selected increases. Research on the zero-price effect includes the classic zero-price effect, the zero-price effect in bundled promotion, and the zero-price effect in freemium. The zero-comparison effect means that when the desirable attribute of a product shifts from a small non-zero number to zero, the proportion of this product being selected increases, and when the undesirable attribute of a product shifts from a small non-zero number to zero, the proportion of this product being selected decreases.
The current literature further focuses on the mechanisms underlying the zero-price effect and the zero-comparison effect. Affect and social norms are two psychological mechanisms to explain the zero-price effect. The affect perspective holds that the emergence of the zero-price effect includes two processes. In the first process, the free product evokes consumers’ positive affect. In the second process, positive affect makes consumers more inclined to choose the free product, which generates the zero-price effect. The perspective of social norms is another approach to explaining the zero-price effect. The social norms of reciprocity and politeness make consumers more inclined to choose zero-price products, thus resulting in the zero-price effect. Reference dependence is the mechanism to explain the zero-comparison effect. The reference dependence perspective states that people rely on relative differences of a product attribute to make decisions. Since “0” cannot be used for the comparison of relative differences, consumers thus lose the reference point, which makes it hard to identify relative differences of a given product attribute, thereby lowering the influence of relative attribute differences on consumers’ decision-making which leads to the zero-comparison effect.
Some studies focus on the boundary conditions of the zero-price effect and the zero-comparison effect. These studies reveal that product price, product type, and consumer psychology are the boundary conditions for the zero-price effect, whereas the number of choice options is the boundary condition for the zero-comparison effect.
We suggest that future research be carried out in the following ways. For the zero-price effect, future research can further explore how product type, social norms influence the zero-price effect. Since price not only symbolizes the monetary cost (sacrifice), but also the product quality, future research can consider the impacts of price-sacrifice and price-quality on the zero-price effect. Moreover, future research on the zero-price effect can concentrate on attention, examining whether the zero-price effect comes from the fact that the zero price attracts more consumer attention. For the zero-comparison effect, future research can be based on structural alignment model and equate-to-differentiate model to further study consumers' “comparison mechanisms” for product attributes and their influences on the zero-comparison effect. Finally, future research may also investigate the association of the zero-price effect and the zero-comparison effect by exploring whether price can be seen as an “undesirable” product attribute.

Key words: consumer decision-making, the zero-price effect, the zero-comparison effect, affect, reference dependence