The effects of an abrupt increase in taxes on sugary products: A difference-in-discontinuity design

The primary aim of this analysis is to identify the effect of an increase in the Norwegian taxes on chocolate and sugar products and non-alcoholic beverages on sales of taxed products. A secondary aim is to evaluate sales of potential substitutes to the taxed products, as a shift to unhealthy substitutes has been reported as a concern when implementing taxes on unhealthy food and sugar sweetened beverages. While minuscule adjustments in these taxes happens January 1st yearly, our interest lies in a large jump January 1st 2018. From January 1st 2018 there was an increase of 80 and 40% in the taxes on (1) chocolate and sugar products and (2) non-alcoholic beverages, respectively. Our analysis is based on retail data from the Nielsen company, and consists of grocery stores sales data (value, volume and number of items) as registered at the cash register and aggregated by product category, shop and week.