Last week, itbestofbreed.com published a blog about unlimited time off policies, like the one announced to much fanfare by Virgin founder Richard Branson.

Research cited in a Business Insider blog Tuesday quantifies the cost of the American work ethic, and it seems that putting window dressing on the company culture might be the most important thing your time off policy does.

Whether you want to be seen as a company where people work virtually all the time from wherever they want but get an unlimited number of days off, or as a more traditional firm that grants two or three weeks of paid time off, American workers just aren't that into vacation time, and that's good for you as an employer. However, stats like the following have to make you wonder about how long workers will shrug off vacation days.

By not using all their vacation days, American workers left some $52.4 billion on the table in 2013, according to research cited by Business Insider. American workers used an average of 16 vacation days that year, and that number has been falling for nearly a generation. In 1981, workers took an average of 21.1 days off.