• by Laurie Sullivan  @lauriesullivan, March 19, 2014

Mobile devices will account for 50% of Google paid-search clicks by December 2015, according to Marin Software. The company predicts in a report released Wednesday that mobile will become the primary channel for search as investment in these devices increases, surpassing 42% this year.

Marin found the conversion rate of search ads on mobile devices rose in the U.S. during 2013, indicating that consumers are more comfortable with mobile commerce. The conversion rates of smartphones and tablets rose 57% and 67%, respectively. In 2013, tablet conversion rates at 5.5% edged out desktop conversion rates at 5.3% for the first time.

In 2013, the share of paid-search clicks from mobile devices increased from 21.8% to 34.2% of all paid-search clicks. The percentage that marketers spent on mobile campaigns saw a similar increases, with mobile spend share rising 45% from 19.3% to 27.9% last year.

While the average cost per click of search ads on smartphones and tablets remained lower than desktop CPCs, Marin found in 2013 that smartphone CPCs rose 21%; and tablet CPCs, 23%. The increase in smartphone and tablet CPCs points to growing competition among mobile advertisers, according to the company.

The benchmark report, Mobile Search Advertising Around the Globe: 2014 Annual Report, analyzes statistics and trends revealed in the Marin Global Online Advertising Index. 

The index consists of advertising data from global brands that manage more than $6 billion in annualized paid-search spend through Marin's platform. The data represents all major industry sectors and 13 countries and regions, including the United States, the United Kingdom, the Eurozone, Japan, and China.