Here's a grinchy kind of report (well, not so grinchy if you're the boss) that says online holiday shopping could cost corporate America half a billion dollars in lost productivity this year.

Philadelphia-based Pearl Software says that it arrived at its estimate by calculating the number of Americans who use the Web at work -- 42 million, according to Nielsen/NetRatings -- and multiplying it by the mean hourly wage of $12.64 for office and administrative workers, provided by the U.S. Bureau of Labor Statistics.

"If every employee with Internet access at work spends a mere hour in online shopping during the month of December, productivity costs to U.S. businesses could surpass half a billion dollars," said David A. Fertell, CEO of Pearl Software.

And, "Given that office and administrative workers' hourly wage is on the lower end of all hourly wages calculated by the Bureau of Labor, a half-billion dollar productivity price tag may even be on the low side," Fertell said.

According to a recent study by the Atlas Institute, weekdays are the most active online shopping days during the holidays, peaking around 1 p.m. Eastern Standard Time. The study even recommends that retailers tailor holiday ads to people in the workplace to best reach online customers.

Of course, this report serves to help promote Pearl Software's Pearl Echo Internet management tool to monitor employees. But in the spirit of the holidays, the company said that many customers use the software to control how employees use the Net. For example, with Pearl Echo you can set up access to shopping sites during lunchtime or after work."