A new study claims that the mobile Web extends the audience reach of major Internet sites by an average of 13 percent over home PC traffic.

The percentage for categories such as weather and entertainment are even higher, at 22 percent, according to Nielson Co.'s newly launched TotalWeb report. The findings were for the fourth quarter of 2007.

"It's a hint into the future of what Internet consumption will look like," said Nic Covey, Chicago-based director of insights at Nielsen Mobile.

"We believe mobile Internet will continue to grow and Internet users will increasingly augment or substitute their PC Internet access with over the phone," he said.

TotalWeb is a new report from Nielsen that combines data from Nielsen Mobile and Nielsen Online to show the unduplicated, unique audience for more than 200 key Internet sites across the PC and Internet areas.

Mobile gives a hand
The weather category obviously gets a lift from the mobile Web simply because there are consumers who access those sites over the mobile phone but not on their home computer.

For example, AccuWeather.com got a 43 percent audience lift from mobile Web users.

Shopping sites, on the other hand, have a duplicated audience. Mobile consumers who visit shopping sites on their mobile phone are also likely to conduct the activity on their home PC.

The report showed that games and music each got a 15 percent average online audience lift from the mobile Web.

The mobile Web extended the audience reach for email by 11 percent, sports 10 percent and the business/finance category by 4 percent.

Search garnered a 2 percent average online audience lift from the mobile Web and shopping/auctions 1 percent.

The data prove that the mobile Internet not only increases the frequency of visits to a Web site, but also grows the overall size of the pie, Nielsen said.

Based on this behavior, publishers can monetize their total cross-platform audience, the market researcher said. Advertisers will also be able to better understand the efficiency and incremental value of mobile Web traffic.

Nielsen estimates that 87 million U.S. mobile users subscribe to mobile Internet services. Also, more than one in 10, or 13.7 percent of, mobile subscribers actively uses the mobile Internet each month.

"The implication for marketers is now when they're looking for an opportunity to partner with a Web site PC presence and also their mobile presence, they can know what the additional value is of that mobile audience," Mr. Covey said.

"So now we know what just added frequency that mobile provides, but we also know what the added reach is and it's substantial," he said.