Rationalizing Declining Grocery Shopping Frequency

Households have decreased their grocery shopping frequency from once every 4.7 days in 1998 to once every 6.3 days in 2009. To understand this change, an optimal control model is developed of a utility maximizing household that chooses when to shop, how much to purchase, and their piece wise continuous consumption paths. The model is calibrated to U.S. data to identify the decay rate of households' food baskets required to rationalize the change in shopping frequency. The implied decay rates are highly correlated with per capita consumption of fresh fruits of vegetables. It is concluded that 72% of the change in shopping frequency is attributed to changes in food choice, with the remaining 28% attributed to increased fixed costs of making a shopping trip. The public health consequences of declining food decay rates are considered, and it is recommended that changes in shopping frequency be used as an indicator of changes in diet