Work productivity notoriously dips during the winter holiday season but a survey released yesterday suggests that employee productivity takes a nosedive for an entire month surrounding Christmas.

Whether it's due to laziness, vacation time or other factors, productivity begins dropping during the two-week period before Christmas, according to a survey of computer usage by Glance Networks, a maker of web demos software. Based on past trends, productivity will begin its annual pre-Christmas drop this week, said Rich Baker, founder and chief executive of the US company.

"It's striking," Baker said. "We looked at the last three years and the trends were almost identical year to year...[Employees are] not doing as much business-oriented work."

The survey found that productivity declined steadily for two weeks leading up to Christmas, and was 35 percent below normal levels on Christmas Eve. Productivity was down nearly 90 percent the day after Christmas, and 50 percent below normal levels until New Year's Day.

Most employees did not return to pre-holiday levels of productivity until the third Tuesday after New Year, the company said.

The trend may not be due to simple laziness. Clearly, employees use more holiday time during the winter holiday season. Baker said Glance Networks did not try to determine what factors cause the annual drop in productivity.

"It could just be employees taking time off. All I can say is [work-related web] traffic is down," he said.