Facebook is offering advertisers CPC rates discounted by as much as 45% to book campaigns that encourage users to remain within the social network, according to research from TBG Digital.  

The strategy, where Facebook offers discounts of up to 45% on ads that keep users within the social network compared with those that direct traffic away from the site, has helped it increase ad revenue by 23% compared to the beginning of 2011.  

TBG Digital’s Q4 Global Facebook Advertising report, based on 326bn impressions and verified by the University of Cambridge, also found that advert performances, such as click-through rates, also improved 18% throughout 2011.

TBG Digital’s report also claimed that  CPM rates on the social network increased by 8% on average over the quarter.

The top five industry verticals, by volume, to advertise on Facebook were:  finance, retail, food and drink, games and entertainment, according to the study.

Brands from these sectors accounted for almost 70% of the total ads served on Facebook, with internet and telecoms brands closely behind.

Campaigns by food and drink brands recorded the highest CTR levels, according to TBG.

Simon Mansell, CEO of TBG Digital, said, “The potential cost savings available by maintaining traffic within the Facebook environment is particularly compelling and demonstrates its effectiveness as an advertising channel and also as a ‘destination’, with more and more clients investing heavily into their Facebook presence.”

Mansell also forecast that Facebook’s advertising revenue would increase further throughout 2012 as the social network is reportedly set to introduce mobile ad formats in the early part of this year.