NEW YORK—Interpublic Group PR firms Weber Shandwick and GolinHarris have grown amid a third quarter decline in the CMG group that houses them.

Interpublic's Constituency Management Group (CMG), within which most of its PR firms are held, saw revenues slide by two percent on an organic basis to $329.5m, because of a spike in Olympics-related project activity during the same period one year earlier.

On an earnings call, Interpublic CEO Michael Roth noted that "the very strong performance of our public relations agencies continued in the quarter," pointing in particular to Weber Shandwick and GolinHarris, "which continue to win market share, domestically and internationally."

Given the nature of the Olympics activity, it is understood that the CMG decline likely impacted event firm Jack Morton and sports agency Octagon, although Interpublic does not break out revenue performance for specific firms.

For the year to date, CMG firms have grown 6.4 percent on an organic basis.