(charts by quantcast.com)

iPad users are using Apple's newest device to surf the web so much that it accounted for over five percent of mobile web traffic on its launch day. At least, that's what Quantcast Corporation, a web analytics outfit based in San Francisco and New York, said in a blog post last week.

The company posted a chart depicting iPad traffic back to March 18. They said they saw traffic that early, but since the iPad hadn't shipped yet, the volume of the traffic doesn't show up on the chart.

"To hit 5% of mobile web consumption in the first full day of usage is astounding, and creates a challenge for this form of analysis," the unsigned post in the company's blog said.

Quantcast said in the future that it would exclude the iPad from its mobile analysis, citing the way it blurs the line between conventional and mobile computing. They speculated that many people with iPads might leave them at home while carrying an iPhone in their pockets.

The company said it would continue to measure iPad web traffic, though for now the iPad won't be classed as a mobile device in its reports.

Quantcast says it "engages all 220 million U.S. Internet users" to make detailed audience proviles for advertisers.

In a chart posted at the end of the blog entry, Quantcast compared a chart of Apple mobile devices, comparing their share of traffic with each other for a 7-day period ending March 6.

During that time, the iPad gained 7 points, while the iPhone lost about 5 points and the iPod touch lost about 2 points, according to the chart. The chart didn't say whether all traffic originating from Apple devices increased or decreased during the period.