Kersbergen Inge, Copeland Amber, Pryce Robert, Meier Petra, Field Matt
School of Medicine and Population Health, University of Sheffield, UK.
Department of Psychology, University of Sheffield, UK.
Addiction. 2025 May;120(5):860-870. doi: 10.1111/add.16723. Epub 2024 Dec 3.
Buying smaller-sized alcohol products can reduce alcohol consumption, but larger products have better value for money, which presents a barrier to switching. We tested whether proportional pricing prompts drinkers to buy smaller alcohol products and reduce alcohol purchasing.
DESIGN, SETTING AND PARTICIPANTS: This study was an online experiment set in the United Kingdom, using hypothetical shopping tasks in which participants purchased different-sized products presented under proportional pricing (i.e. constant price per litre throughout all sizes of the same product) or standard pricing conditions. Study 1 (comprising n = 210 participants) was a mixed experiment with pricing condition (proportional pricing, standard pricing; within-subjects) and drink type (lager, red wine, vodka; between-subjects) as manipulated factors. Study 2 (comprising n = 90 participants) was a within-subjects experiment with pricing condition (proportional pricing, standard pricing) and multi-pack type (size difference-only, quantity-difference only, size and quantity difference) as manipulated factors. Participants were UK adult alcohol consumers.
We measured outcome variables, including alcohol purchasing (UK units) and proportion of alcohol purchased from smaller products.
Proportional pricing consistently increased the proportion of alcohol purchased from smaller products [study 1: B = 10.82, 95% confidence interval (CI) = 8.72-12.92; study 2: B = 11.64, 95% CI = 3.50-19.77], indicating a switch to smaller products. However, this did not consistently reduce the total amount of alcohol purchased among drink and product types: proportional pricing reduced the total units purchased from lager multi-packs containing more rather than fewer products (B = -2.56, 95% CI = -4.82 to -0.30), but not from other types of lager multi-packs or single lager products. Proportional pricing also reduced vodka purchasing (B = -3.30, 95% CI = -5.21 to -1.40), but the effect of proportional pricing on wine purchasing was moderated by hazardous drinking (B = -0.11, 95% CI = -0.17 to -0.05).
Alcohol sales policies that require proportional pricing may reduce alcohol purchasing.
购买小容量酒精饮品可减少酒精摄入量，但大容量产品性价比更高，这成为了消费者更换选择的障碍。我们测试了按比例定价是否会促使饮酒者购买小容量酒精饮品并减少酒精购买量。
设计、地点与参与者：本研究是一项在英国开展的在线实验，采用虚拟购物任务，让参与者在按比例定价（即同一产品所有容量规格每升价格恒定）或标准定价条件下购买不同容量的产品。研究1（n = 210名参与者）是一项混合实验，将定价条件（按比例定价、标准定价；受试者内）和饮品类型（淡啤酒、红葡萄酒、伏特加；受试者间）作为操控因素。研究2（n = 90名参与者）是一项受试者内实验，将定价条件（按比例定价、标准定价）和多包装类型（仅容量不同、仅数量不同、容量和数量均不同）作为操控因素。参与者为英国成年酒精饮品消费者。
我们测量了结果变量，包括酒精购买量（英国单位）以及从小容量产品购买的酒精占比。
按比例定价持续增加了从小容量产品购买的酒精占比[研究1：B = 10.82，95%置信区间（CI）= 8.72 - 12.92；研究2：B = 11.64，95% CI = 3.50 - 19.77]，表明转向了小容量产品。然而，这并没有始终如一地减少各类饮品和产品类型的酒精购买总量：按比例定价减少了从包含较多而非较少产品的淡啤酒多包装中购买的总单位数（B = -2.56，95% CI = -4.82至 -0.30），但从其他类型的淡啤酒多包装或单瓶淡啤酒产品中购买的总量并未减少。按比例定价也减少了伏特加的购买量（B = -3.30，95% CI = -5.21至 -1.40），但按比例定价对葡萄酒购买量的影响因危险饮酒情况而异（B = -0.11，95% CI = -0.17至 -0.05）。
要求按比例定价的酒精销售政策可能会减少酒精购买量。
