The impact of taxation and signposting on diet: an online field study with breakfast cereals and soft drinks

We present a large scale study where a nationally representative sample of 1000 participants were asked to make real purchases within an online supermarket platform. The study captured the effect of price changes, and of the signposting of such changes, for breakfast cereals and soft drinks. We find that such taxes are an effective means of altering food purchasing, with a 20% rate being sufficient to make a significant impact if (and only if) the tax is signposted. Signposting represents a complementary “nudge” policy that could enhance the impact of the tax, though its effectiveness depends on the product category.