Before 2014, Chile had a 13 percent sales tax on drinks regardless of their content. Then, a 2014 law increased sales tax for sugary drinks to 18 percent, and lowered the tax for non-sugary drinks to 10 percent. Chile defined “sugary” drinks as those with 6.25 grams or more of sugar per 100 milliliters of liquid, and non-sugary ones below that threshold.

The idea was to give consumers an incentive to choose the healthier option, especially among groups with lower incomes, who tend to drink more sugary drinks.

By using shopping data from three years before the tax and one year after the tax, researchers found that purchasing trends did change. On average, people in Chile purchased 21.6 percent less sugary drink by volume. Surprisingly, the tax more profoundly affected high socioeconomic groups, who purchased 31 percent less sugary drink. Low socioeconomic groups purchased only 12 percent less.