$9 out of every $100 e-commerce dollars spent in the United States between January and June were spent on mobile devices. That's according to digital market research firm comScore who recently published a research note on m-commerce spending in the U.S.

In total, Americans spent more than $10 billion shopping on their mobile devices in the first half of 2013, putting mobile spending on track to reach at least $25 billion this year. The lion's share of m-commerce spending happens on smartphones, which is owed to the simple fact that there smartphone users outnumber tablet users significantly. In fact, average spending per user is 20 percent higher on tablets, notes comScore.