"The University of Melbourne study showed that people who use the Internet for personal reasons at work are about 9 percent more productive that those who do not.
... Coker said the study looked at people who browsed in moderation, or were on the Internet for less than 20 percent of their total time in the office.
Caveat: "Those who behave with Internet addiction tendencies will have a lower productivity than those without," he said."
The employees of my daughter's orthodontist here in America aren't allowed to access the internet, probably for fear of some sort of contagious or distracting "internet addiction." What a throwback to an earlier era. More likely, it would keep them awake and alert. And, as this Australian study says, increase their productivity.