The recent flurry of agency acquisitions will likely continue in the next year, especially in terms of specialist or international firms, said agency executives and M&A experts.

A primary reason is that specialized agencies are typically a more opportunistic acquisition than general PR firms, explains Harris Diamond, CEO of Interpublic Group's Constituency Management Group. CMG, which includes PR firms Weber Shandwick and GolinHarris, has made a number of acquisitions this year, mostly outside the US.

“Specialist agencies often offer a ...