NEW YORK: Agencies in the US posted an increase in revenues of 3.7% last year to $33.7 billion (€25.6bn; £23.1bn), although this figure included a decline of 0.1% in the second half of 2008 in real terms, according to figures from Advertising Age.

In its latest annual Agency Report, Ad Age assessed revenue levels across agencies in the advertising, healthcare, marketing and media services sectors.

DDB Worldwide, part of Omnicom Group, and McCann Worldgroup, owned by Interpublic Group, were found to be the best-performing networks, both posting global revenues of around $2.8bn.

WPP was the top holding company on this measure, recording sales of $13.6bn in 2008, a figure that would have risen to $15.4bn if taken to include annual revenues from TNS, which the marketing services conglomerate purchased in October last year.

Omnicom was in second place on $13.36bn, followed by Interpublic with $6.96bn, and Publicis on $6.9bn.

The share of total US agency revenues enjoyed by the "big four" also rose to 49.2% last year, up by 3.8% on an annual basis.

Digital agencies posted a 14.8% upturn in revenues in 2008, with the "big four" holding companies now deriving 16% of their sales from this medium, an increase of 3.7% year-on-year.

Some 60% of US agencies assessed also now report digital revenues, indicating an increased level of penetration of the medium across the industry.

However, charting figures since 2001, Ad Age found that the total growth rate across all sectors is now at its lowest level since 2002, having reached a peak of 9% in 2006.

Overall, it estimates that 172,700 people were employed by agencies in February this year, down from around 175,000 in January, and under 188,000 in December 2007.

Data sourced from AdAge; additional content by WARC staff