Research data supporting "Price of change: does a small alteration to the price of meat and vegetarian options affect their sales?"

Abstract

This research data file contains data from a study conducted autumn term 2018 on vegetarian, meat, fish and vegan sales, total sales; summaries of individual meal selections, and model estimates from a college cafeterias at the University of Cambridge. The aim of the study was to investigate the impact of a small change in price on vegetarian sales, meat sales and overall sales. The vegetarian option price decreased by 20p from £2.05 to £1.85, and meat option price increased by 20p from £2.52 to £2.72. The study comprised of 106 mealtimes with 13,840 meal selections. We summarized the sales transaction data into 1) aggregate data, summarizing the total vegetarian, meat, vegan and fish meal sales at each lunch and dinner and 2) individual-level data on whether each diner at a meal selected a vegetarian, meat, fish or vegan meal. Purchases made with university cards enabled anonymized individual diner-level purchases to be tracked; this is useful in evaluating how diners with different pre-study levels of purchasing vegetarian&vegan meals responded to the change in price. We used the total number of meals sold at a mealtime to analyse total sales. We estimated the effect of the price change on vegetarian, meat and total meal sales, adjusting for other predetermined variables, including day of the week, ambient temperature, and time since the start of the study. We used linear models (LMs) and binomial generalized linear models (GLMs) for aggregate data. Binomial generalized linear mixed models (GLMMs) were used for the individual-level data, with individual diner fitted as a random effect, which allows each diner to have a different likelihood of selecting a vegetarian meal. A 95% confidence level was used to calculate confidence intervals (CIs). Models were evaluated using model diagnostics.