Bourbon drinkers are the best tippers, and those who drink cordials keep the tightest grip on their wallet, according to a study of liquor sales by Restaurant Sciences.

Bourbon drinkers tip an average of 22.69 percent, while those who drink cordials, which are sweetened liquors most often served after dinner, tip an average of 19.66 percent, Restaurant Sciences said. Also among those who tip 22 percent or more on average were those who drink blended whiskey and cider. Also among those who tip less than 22 percent were those who drink gin, vodka, rum and scotch.

Massachusetts-based Restaurant Sciences, which provides analysis and research to the food services industry, said it analyzed more than 4 million checks from restaurants and bars in its study, details of which a spokeswoman said were available only to its clients.