After a bleak 2009, global marketing research firms are on an upward trajectory, reports the American Marketing Association (AMA).

The world's 25 largest marketing research conglomerates had total revenues of$18.8 billionin 2010 -- up 4.9% from the previous year, according to the Honomichl Global Top 25 Report, publishedAug. 30in AMA's Marketing News magazine. (Adjusted for inflation, the gain was 3.2%.)

Payroll on the international research front followed suit: The top 25 firms employed 107,803 people full-time in 2010, up 4.4% from the year before.

"While the global research industry's 2010 revenue growth was healthy -- and most welcome -- it was not enough to recover the downside of 2009," saysJack Honomichl, founder of the newsletter "Inside Research," who compiles the annual Honomichl ranking with colleagueLarry Gold. (The top 25 firms' real growth in 2009 was -4.5%.)

"Further, seven of this year's Global Top 25 firms' revenues decreased from 2009 to 2010 or did not grow enough to cover inflation," Honomichl says, adding that U.S.-based firms and smaller firms tended to lag behind the others.

Still, the overall positive trend is encouraging, and Honomichl says it appears to be continuing in 2011. The 25 leading firms account for approximately 63% of spending on marketing, advertising and public opinion research services worldwide, he points out. "Their financial health is of special importance. They are the industry's backbone."

The top five firms -- The Nielsen Co., Kantar, IMS Health Inc., GfK SE and Ipsos SA -- each had revenues of$1 billionor more, together representing 72% of the top 25 firms' total revenue.