From Staff and Wire Reports

NEW YORK, N.Y. – Research firm eMarketer says it expects worldwide spending on mobile advertising to reach $31.5 billion this year, a 75 percent increase from 2013.

By the end of this year, eMarketer says mobile will account for nearly a quarter of total digital ad spending. Read full report.

Mobile ad spending has been growing fast, mainly due to ad revenue growth at Facebook and Google.

In 2013, mobile ad spending more than doubled, to nearly $18 billion from $8.8 billion in 2012. Facebook and Google together saw an increase of $6.9 billion in mobile ad revenue.

eMarketer bases all of their forecasts on a multipronged approach that focuses on both worldwide and local trends in the economy, technology and population, along with company-, product-, country- and demographic-specific trends, and trends in specific consumer behaviors.They also analyze quantitative and qualitative data from a variety of research firms, government agencies, media outlets and company reports, weighting each piece of information.

EMarketer expects Facebook’s share of the mobile ad market to grow to 21.7 percent this year from 17.5 percent in 2013, taking a bite out of Google’s share, though Google remains No. 1.