The results of a GSMA-led study were released today, offering the advertising community a window into mobile audience metrics.

The study was based on anonymous data from U.K. mobile operators and compared mobile users' internet activity to the web browsing habits of PC users. Advertisers may be interested to find that 48 percent of the study's mobile users were 18-34-year-olds, while mobile also appeared to be more popular with men, who represented 63 percent of total users.

Results of the study indicated that 68 percent of the users visited mobile operator portals most often, while Google was the most popular off-portal site. Facebook was the site where mobile users spent the most time browsing, according to data compiled by comScore. Furthermore, users spent an average of 24 minutes daily on Facebook, not much less than the average of 27.5 minutes spent by PC users. However, mobile users visited Facebook more frequently, with 3.3 daily visits, compared to 2.3 daily visits by PC users.

The study also found that mobile users most often browsed the web in the early morning, from 7 a.m. to 10 a.m., which represented 22 percent of their daily mobile browsing time. In contrast, PC users only spent 11 percent of their total web browsing time in this period.

"This major mobile advertising initiative, as outlined today by the GSMA in Barcelona, is a large validation that the mobile advertising industry is a key global growth area in mobile," said Paul Palmieri, president and CEO of Millennial Media. "We wholeheartedly agree that data, and further refinement of standard metrics are the key to unlocking the brand advertising dollars that will power the growth of the overall mobile advertising industry."