Liquor prices tend to be higher in states with a monopoly over liquor sales compared with states without control over alcohol prices, a new study finds.

Researchers at the Boston University School of Public Health found that the average price of liquor was $2 lower in states that do not control liquor sales, compared with so-called control states.

Reuters reports that as of February 2012, there were 18 states that set the price of liquor sold to retail stores, and 13 of those states also set the price for the general public. The remaining states sell liquor licenses to private business owners, who in turn set their own prices.

The researchers note in the journal Addiction that states that control liquor prices tend to make more money from liquor sales.

Lead author Dr. Michael Siegel, a researcher from the Boston University School of Public Health, told Reuters that price differences between control states and license states may influence how people drink. “There is convincing evidence in the literature that control states have lower alcohol consumption than the license states,” he said.