Yahoo ranked as the top US internet property based on the number of display ad impressions delivered in November, according to statistics from comScore.

The research firm explained that one way of understanding a site's ability to monetise its content is the number of display ads it serves.

Fox Interactive served the most display ads per user visit to its sites in November at 47.5, followed by Bebo (27.2), CBS Sports (22.6), Viacom Digital (20.6) and Yahoo (20.5).

But Yahoo claimed 18.8 per cent of all US display ad views, beating Fox Interactive (16.3 per cent), Microsoft Sites (6.7 per cent), Time Warner Network (5.8 per cent) and Facebook (1.5 per cent).

ComScore said that nearly half of all display ads seen by US internet users originate on just five properties, illustrating the concentration of advertising among a few sites.

Display ads are defined as any rich media or static image served and loaded into a web browser, but do not include video streams, text or paid search ad impressions.

Alistair Sutcliffe, vice president of comScore Advertising Solutions, said: "Just a handful of publisher properties deliver a preponderance of display ads.

"When one goes beyond the top properties it is clear how fragmented the online advertising market is, underscoring the importance of advertising networks in aggregating the long tail."