In-store food promotions increase sales as well as household food waste.

Food waste is a serious problem affecting both global food security and climate change. Using a large-scale field experiment with data from 43,246 perishable vegetable purchases from eight supermarkets, we show that in-store offers lead to over-purchasing of food items and result in an increase in household food waste. Shoppers exposed to multi-unit offers (e.g., "2 for $5" or two-for-one pricing) purchase greater food quantities compared to those exposed to a single-unit discounts (e.g., "$2.50, regular price $2.89" or "50% off"). A follow-up survey shows that these additional items are subsequently less likely to be consumed, leading to an increase in household food waste. A complementary online survey provides further support for these results. Importantly, as a part of the field experiment, we test two strategies that can address in-store over-purchasing. Taken together, the current findings provide important insights into factors that increase over-purchasing and household food waste, as well as strategies that can help overcome them. We thus demonstrate how retailers can negatively, but also positively, impact important societal and environmental causes.