The number of people who took to the mouse before leaving the house for Black Friday shopping increased significantly this year, according to an Internet ratings service.

Those shopping from a home Internet connection the Friday after Thanksgiving increased 29 percent from last year, Nielsen/Netratings, an Internet-traffic-monitoring service, said Monday.

The service recorded 17.2 million “unique visitors” at more than 100 representative online retailers Friday, compared with 13.3 million on Black Friday 2004.

Yahoo Shopping, the retail arm of the gargantuan Web portal, said visitors to its site rose 52 percent Friday, better than the 30 percent jump it had expected.

Besides Black Friday – the traditional start of the winter holiday-shopping season – retail observers have added the phrase “Cyber Monday” to their lexicon.

Internet-traffic monitor Akamai Networks in Cambridge, Mass., ran a real-time, global Internet traffic watch on its Web site Monday, and said the day appeared to be a record-breaker. And employers might be chagrined to know that they subsidized much of the Web-surfing and -shopping activity.

Visits to online retailers peak Monday afternoons, presumably when people are still at work, said Jennifer Donovan, an Akamai spokeswoman.