Each year, employers lose an average of $255 in productivity per employee to something called "presenteeism," according to a 2004 study published in the Journal of Occupational and Environmental Medicine. Multiply that number by your entire workforce and your business may be facing significant losses. But what is presenteeism, and how is it robbing your employees of so much productivity?

There's no one agreed-upon definition, though in 2004, Paul Hemp wrote in the Harvard Business Review that it is "the problem of workers' being on the job but, because of illness or other medical conditions, not fully functioning." In many ways, it is a stealthier version of absenteeism, when workers simply do not show up. But unlike employee absences, which are easily checked and recorded, employees who are ill, distracted, or depressed may still show up at work, though their productivity is reduced, and go through the motions of their jobs. These impaired employees are more apt to make mistakes, miss deadlines, or in worst case scenarios, cause accidents on the job.