Mobile traffic currently makes up 10% of global Internet traffic, as shown in the chart, and next year more people will use mobile phones than PCs to get online, according to Gartner. Purchases made on mobile devices amounted to $6.7 billion in the U.S. last year, or about 8% of total online sales, and are expected to nearly double to $11.6 billion this year. By 2015, U.S. mobile sales are forecast to reach $31 billion.