There were more than 450 million mobile Internet users worldwide in 2009, a number that is expected to more than double by the end of 2013. Driven by the popularity and affordability of mobile phones, smartphones, and other wireless devices, IDC expects the number of mobile devices accessing the Internet to surpass the one billion mark over the next four years.

“The number of mobile devices with Internet access has simply exploded over the last several years,” says John Gantz, chief research officer at IDC. “With a wealth of information and services available from almost anywhere, Internet-connected mobile devices are reshaping the way we go about our personal and professional lives. With an explosion in applications for mobile devices underway, the next several years will witness another sea change in the way users interact with the Internet and further blur the lines between personal and professional.”

The most popular online activities of mobile Internet users are similar to those of other Internet users: using search engines, reading news and sports information, downloading music and videos, and sending/receiving email and instant messages. Over the next four years, IDC expects some of the fastest growing applications for mobile Internet users will be making online purchases, participating in online communities, and creating blogs. Accessing online business applications and corporate email systems is also expected grow rapidly as businesses move to empower their mobile workforce.

Highlights from IDC’s Worldwide Digital Marketplace Model and Forecast include the following:

• More than 1.6 billion people—a little over a quarter of the world’s population—used the Internet in 2009. By 2013, over 2.2 billion people—more than one third of the world’s population—is expected to be using the Internet.
• More than 1.6 billion devices worldwide were used to access the Internet in 2009, including PCs, mobile phones, and online videogame consoles. By 2013, the total number of devices accessing the Internet will increase to more than 2.7 billion.
• China continues to have more Internet users than any other country, with 359 million in 2009. This number is expected to grow to 566 million by 2013. The United States had 261 million Internet users in 2009, a figure that will reach 280 million in 2013. India will have one of the fastest growing Internet populations, growing almost two-fold between 2009 and 2013.
• Presently, the United States has far more total devices connected to the Internet than any other country. China, however, is the leader in in the number of mobile online devices with almost 85 million mobile devices connected to the Internet in 2009. The number of Internet devices in India, both mobile and fixed, is expected to grow commensurate with the number of Internet users.
• Worldwide, more than 624 million Internet users will make online purchases in 2009, totaling nearly $8 trillion (both business to business and business to consumer). By 2013, worldwide eCommerce transactions will be worth more than $16 trillion.
• Worldwide spending on Internet advertising will total nearly $61 billion in 2009, which is slightly more than 10% of all ad spending across all media. This share is expected to reach almost 15%% by 2013 as Internet ad spending grows surpasses $100 billion worldwide.

IDC’s John Gantz will provide an overview of the data and trends found in the Digital Marketplace Model and Forecast on December 10th at 12:00 pm U.S. Eastern time (details).