It’s time for ad companies to release their year-end forecasts, and ZenithOptimedia is out today with a bullish one – largely tied to big increases it expects for ads on smartphones and tablets. It projects global spending in 2014 to hit $532B – a 5.3% increase vs this year which is +3.6% from 2012. (The new projection is up slightly from the company’s forecast in September for spending to grow 5.1% in 2014.) The Winter Olympics and mid-term elections should propel spending in North America 4.6% from this year’s $166.9B, which is +3.3% vs 2012. But mobile is the big story. The medium “is now the main driver of global adspend growth,” it says. “This is the first time in the past 20 years that a new platform is expanding overall media consumption without cannibalizing any of the other media platforms.” By 2016 mobile should become the fourth largest ad medium, ahead of radio, outdoor and magazines, ZenithOptimedia says. This is the first time the company also has made some three-year projections. It says that global spending on mobile will hit $45.4B in 2016, up from $13.5B this year. In the U.S. ad sales for mobile display will increase 239.4% by 2016 to $6.4B. Smartphone penetration will grow to 77.3% from 54% in 2013, while 37.1% will own tablets, up from 23.8%. Over the same period, global ad sales on television will increase by $29.8B, but its market share will slip to 39.3% in 2016 from a peak of 40.2% this year. ZenithOptimedia will join other ad firms to discuss their forecasts in more detail on Monday at the UBS Annual Global Media and Communications Conference.