With elections in the United States and the Summer Olympic Games across the Atlantic pond in London this year, U.S. ad spending is expected to continue a strong growth throughout 2012, according to eMarketer. The digital marketing analysis firm estimates that search spending will jump up to $19.5 billion, which is a 27.9% increase from last year. In the upcoming years, however, search ad spending is expected to slow down although the total amount spent will likely near the $30 billion mark by 2016.

As if this is any surprise to anyone in the Internet know, Google’s revenues will continue to grow in 2012 but eMarketer expects that Microsoft will eventually surpass Google’s growth rate 2013 and 2014. Still, they point out, by that time Google will command 10 times the search ad revenue that Microsoft will claim.

Even with Microsoft’s greater growth rate in the next few years, Google will undoubtedly remain atop the search ad market in the United States. eMarketer expects that Google will collect 77.9% of all U.S. search ad revenues this year and, by 2014, its total market share will be 79.8%. In a bit of good news for Microsoft, who seems to be a fatal second place to Google in search ad revenue, eMarketer anticipates that the company will pull further ahead from Yahoo! and AOL as both of the latter companies are expected to lose “more than half” of their search ad revenues between 2011 and 2014.

Given that Google’s ad revenue growth over the next three years is expected to drop off precipitously, I wonder if it’s just a symptom of Google peaking. There’s only so much you can advertise, right? Then again, maybe since this is a big year for commercialized events (U.S. elections, Summer Olympics) the next couple of years might just be “off” years until 2014 when the World Cup begins in Brazil and the Winter Olympics in Russia.