Online has become the fourth-largest display advertising market in the U.K. as media consumption shifts, especially among those age 16-24, according to a report by the U.K. Office of Communications (Ofcom).

Online advertising revenue totaled 1.3 billion pounds last year, and online is now worth three times the radio advertising market, according to Ofcom's annual communications market report, ZDNet writes. Online is now fourth in the U.K. behind newspapers, TV and direct mail, having overtaken outdoor in 2005 - and also the business magazine and consumer magazine markets.

The trend is in part the result of more people using broadband internet more and traditional media less, particularly the 16-24 age bracket; some 70 percent of internet users in that age group engage in social networking and blogging - half of them at least weekly.

Total online advertising revenues have increased almost eight-fold in real terms between 2001 and 2005 (from 0.17 billion pounds to 1.3 billion per year), Ofcom said. Online advertising revenue is now almost three times greater than radio advertising revenue (at around 0.5 billion pounds, unchanged since 2001 in real terms) and over one-third that of television advertising revenue (3.8 billion pounds in 2005, up from 3.5 billion in 2001).

Of the 11.1 million U.K. homes and small businesses with broadband connections, more than three million were cable and eight million were DSL in 2005. The number of Wi-Fi hotspots across the U.K. almost doubled over the year to June 2006, up from 8,500 to 14,600.