If you're a U.S. worker, there's a 10 percent chance that you work from home at least once a week, and a 4.3 percent chance that you work from home most of the time. And if you're one of those working from home, you're likely a more productive worker, at least according to a study recently published by Stanford.

More employees working from home than ever before, and yet widespread skepticism about the practice remains. Policies vary wildly from company to company, even within the same industry. For example, according to the paper, JetBlue's call center employees work from home the vast majority of the time, but Delta and Southwest have no work-from-home program.

To study whether employees are more or less productive at home or in the office, the researchers created perhaps the first randomized study of remote work at Ctrip, a travel agency in Shanghai, China with 13,000 employees. One of the co-authors of the paper, James Liang, actually used to be the CEO of Ctrip and was still the chairman at the time of the study, giving the team unique access and insight into the company's management strategies.

Ctrip was concerned about the rising costs of office space, and a 50 percent annual attrition rate. The company found 255 employees in its airfare and hotel divisions who both wanted to work from home and met a few requirements to do so. (They had worked for the company for at least 6 months, had broadband access at home and a private room to work from.) The researchers then split those 255 volunteers into two groups: those with even-numbered birthdays would work from home four out of five days a week, those with odd-numbered birthdays stayed in the office. Employees who worked from home had the same supervisors (who were all office-based) and worked the same shifts as their counterparts to ensure a direct comparison.

During the 9-month study they found:

A 12 percent increase in productivity for the at-home workers. Of that increase, 8.5 percent came from working more hours (due to shorter breaks and fewer sick days) and 3.5 percent came from more performance per minute. The researchers speculate this was due to quieter working conditions.

No negative spill-overs to the control group stuck in the office even though they had communicated that they wanted to work from home.

A 50 percent decrease in attrition among the work-from-home group.

Substantially higher work satisfaction as measured by a survey among the home group .

After the study was over, Ctrip offered all qualified employees across the company the opportunity to work from home. The researchers continued tracking stats for a few more months and noticed something interesting: Employees who were already more productive tended to chose working from home while less-productive employees chose to stay in the office. That suggests that not only will letting call center workers work from home increase their productivity, it may also help attract (and retain) better workers.

The results might not map perfectly to other types of knowledge work. Call centers not only provide an easy way to monitor productivity, but a steady flow of tasks. More fluid or self-directed forms of work, such as software development, are more difficult to measure and may present more opportunities for distraction.