You're addicted to your smartphone. Increasingly, Madison Avenue is too.

We're in the midst of a great migration of ad dollars away from print media to digital devices. While that process is far from over, it will hit a significant milestone this year as smartphones and tablets surpass newspapers, magazines and radio in terms of ad spending.

Research firm eMarketer predicts mobile will account for 10 percent of ad spending by the end of 2014, making it the third-largest ad medium in the U.S. behind TV and PCs. Advertisers are expected to spend an additional 83 percent on mobile this year, an increase of $8.9 billion to $17.73 billion. Newspapers' share of U.S. ad revenues will fall to 9.3 percent from 10.2 percent a year ago. Magazines and radio are roughly stable at 8.5 percent and 8.6 percent, respectively.

The vast majority of U.S. ad dollars pours into television, which is why digital players like Google (NASDAQ:GOOG) and Yahoo (NASDAQ:YHOO) are investing so much in video. Advertisers are expected to spend an additional 3.3 percent on TV in 2014, bringing total spending to $68.54 billion.

The reason dollars are shifting to mobile is that's where user eyeballs are shifting, and increasingly staying. U.S. adults will spend an average of two hours and 51 minutes per day with mobile devices this year, up from two hours and 19 minutes in 2013. 

TV remains the preferred screen, with an average of four hours and 28 minutes, according to eMarketer. But that engagement only begins to tell the story. TV is a big-screen and a sit-back experience, the kind the biggest brand advertisers want.

Mobile is more transactional, so it isn't denting TV but siphoning dollars from search and the Web. Facebook (NASDAQ:FB) and Twitter's (NYSE:TWTR) ad business is already majority-mobile, and mobile is expected to surpass desktop at Google in 2016.

Ad spending estimates Mobile will surpass radio, newspapers and magazines in 2014. Photo: eMarketer