A study put out today by comScore sheds some light on who is doing the majority of the “checking-in” in the U.S.

The statistics were derived from the 16.7 million mobile users than use location-based services and check-in with Facebook Places, Foursquare and Gowalla among others.  That’s 7.1% of the entire mobile population.  Out of those 16.7 million that check-in, 12.7 million of them did it on a smartphone.

The check-in population is split pretty evenly when it comes to sex, with females edging out males by 1.6%.  As far as age, young people are the ones who are doing the bulk of the check-ins.  Users aged 18-24 accounted for 26% of the check-in users and those aged 25-34 accounted for 32.5% of the check-in population.

The majority of check-in service users are employed full-time (46.6%) or a full-time student (23.3%).  Also, check-ins are most frequently taking place on Android and iOS phones.  36.6% of check-in service users do so on Android and 33.7% do so on an iPhone.  When the amount of the total smartphone population each OS represents is taken into account, however, Apple has the higher check-in participation per user.

Not surprisingly, check-in service users are also more likely to access other forms of mobile media.  Nearly 62% of the that specific population accesses news – 40.3% tech news.  Also, 28.2% of check-in service users reported owning a tablet, which is higher than the percentage for all smartphone users (19.6).  Moral of the story: people who check-in are more likely to keep up with new tech.

“Although still in their relative infancy, location-based mobile check-in services are seeing rather impressive adoption among smartphone users,” said Mark Donovan, comScore senior vice president of mobile. “The ability to interact with consumers on this micro-local level through special offers, deals and other incentives provides brands with the real-time opportunity to engage consumers through their mobile device.”

In other check-in news, Beyond recently put out this infographic that shows how social location apps are used by those who have adopted them, why non-users would consider trying them and what people are talking about on the web in terms of location apps.

They found that 90% of users check-in via Facebook places, 22% via Foursquare and 6% via Gowalla.  Of those who do not use location apps, 55% said they would consider using Facebook Places and only 6% would consider using Foursquare.