NEW YORK (TheStreet) - Digital advertising is on the rise and is something investors should be paying attention to. At least, that's what Martin Sorrell, CEO of WPP PLC  (WPPGY) , told TheStreet's Ruben Ramirez. 

WPP, the U.K. based communications services company, reported slightly lower-than-expected revenues in the third quarter. 

WPPGY Chart
WPP plc WPPGY data by YCharts

"Things have tightened up" a bit, Sorrell reasoned, as geopolitical issues -- like Ebola, terrorism in the Middle East, and demonstrations in Hong Kong -- have caused investors to become uncertain. 

"Our clients don't like uncertainty," Sorrell said. But thankfully, many of the current issues from around the world seem to be dissipating to some degree. At least, it seems that way with Russia and Ukraine reaching an energy deal and Japan's increased stimulus program, with the two events helping to ease global concerns.  

Geographically speaking, he said the fastest growing region for the company is the U.K., followed by many of the emerging markets, like Asia, Africa and Latin America. 

These regions are "still dominated by the growth of digital," he explained, with the "most potent force" being mobile ads and mobile search. 

Mobile growth is obviously impressive, especially when investors look at how fast ad revenues are growing for companies like Facebook (FB) , Google (GOOGL)  and Twitter (TWTR) . 

Sorrell said WPP plans to spend $1 billion with Google before the end of the year, on the top of the $2 billion it has already spent in the first nine months of 2014, and $650 million and $100 million with Facebook and Twitter in 2015, respectively. 

Although Google is the clear leader right now, "Facebook and Twitter and other platforms are trying to develop their forms of videos and mobile that will enable them to drive advertising revenues," he concluded. 

-- Written by Bret Kenwell 

Follow @BretKenwell

More from Investing

GE Is Too Opaque, Too Diversified and Too Poorly Managed: Doug Kass Insider

GE Is Too Opaque, Too Diversified and Too Poorly Managed: Doug Kass Insider

GE Rises on Earnings and Revenue Beats Despite Weakness in Power

GE Rises on Earnings and Revenue Beats Despite Weakness in Power

3 Key Things to Watch for in Google's Earnings on Monday

3 Key Things to Watch for in Google's Earnings on Monday

Google's YouTube in Hot Water Again Over Ads on Inappropriate Content

Google's YouTube in Hot Water Again Over Ads on Inappropriate Content

Should Tesla Nominate a New CEO Not Named Elon Musk?

Should Tesla Nominate a New CEO Not Named Elon Musk?