Advertising spending in the U.S. and Canada is expected to grow 4% next year, according to newly released forecast by ad giant ZenithOptimedia.

This year, spending is expected to inch up 3.4% in North America, slowing a bit after last year's infusion of spending to capitalize on viewer interest in the London Olympics, ZenithOptimedia said in its Advertising Expenditures Forecast, released Monday.

"Consumer confidence, retail sales, job numbers and house construction are all trending encouragingly upwards," ZenithOptimedia's report found.

Mobile advertising is fueling the growth. ZenithOptimedia predicts that advertising geared for smartphones and tablets will account for half the total growth in ad expenditures in North America this year. The mobile advertising market is estimated at $6.2 billion. 

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Although it is the fastest-growing segment, mobile ads still represent less than 4% of the total ad spend in North America. 

Internet advertising continues to outpace growth in traditional ad platforms of television and print media.  Television remains marketers' favorite medium, collecting nearly 40% of the total ad spend.

Worldwide ad spending is expected to grow 3.5% this year, surpassing the $500 billion mark -- thanks to a strengthening European economy and continued growth in developing nations, ZenithOptimedia found.

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The firm is predicting larger gains -- 5.1% in 2014 and 5.9% in 2015 -- as European economies continue to stabilize and improve.

Latin America, Asia and Eastern Europe are posting the highest rates of expansion. Commercial spending in Latin America is expected to swell 9.6% this year, while Eastern Europe and Central Asia is on track to notch growth of nearly 11%.

However, the peripheral Eurozone region -- which includes the reeling economies of Greece, Spain, Italy, Portugal and Ireland -- is on track to post a 16% decline this year, ZenithOptimedia found.

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