According to a new forecast from the IDC) Worldwide Quarterly Tablet Tracker, tablet shipments are expected to grow 58.7% year over year in 2013 reaching 229.3 million units, up from 144.5 million units last year. The study predicts tablet shipments will exceed those of portable PCs this year, as the slumping PC market is expected to see negative growth for the second consecutive year. The study also expects tablet shipments to outpace the entire PC market (portables and desktops combined) by 2015.

Ryan Reith, Program Manager for IDC’s Mobility Trackers, says “… tablets surpassing portables in 2013, and total PCs in 2015… significant change in consumer attitudes about compute devices and the applications… for many consumers, a tablet is a simple and elegant solution for core use… previously addressed by the PC.”

The current market expansion has been increasingly fueled by low-cost Android devices, says the report. In 2013, the worldwide average selling price for tablets is expected to decline 10.8% to $381. In comparison, the price of a PC in 2013 is nearly double that at $635. The report projects tablet prices to decline further, allowing a viable computing experience in the hands of many more people at price points the PC industry has strived to meet for years.

Jitesh Ubrani, Research Analyst for the Worldwide Quarterly Tablet Tracker, notes that “… Apple’s success in the education market has proven that tablets can be used as more than just a content consumption or gaming device…  these devices are learning companions… “

Another major shift in the tablet market has occurred around screen sizes, says the report. Apple’s first generation iPad, with a 9.7-inch display, was perceived as the sweet spot for tablets… until 7-inch Android-based tablets began to gain traction in the market. In the space of two quarters the sub-8-inch category exploded to overtake the larger-sized segment in terms of total shipments.

And in the PC market, worldwide PC shipments are now expected to fall by -7.8% in 2013 according to IDC. The new forecast reflects a shift in PC buying trends as users increasingly consider alternatives such as delaying a PC purchase or using tablets and smartphones for more of their computing needs.

In place of a limited decline of -1.3% in 2013 followed by a gradual increase in volume, the new outlook calls for a more substantial decline of -7.8% in 2013 and -1.2% in 2014 with shipment volume reaching only 333 million in 2017, still below the 349 million shipped in 2012 and a peak of more than 363 million shipped in 2011. The updated forecast reflects transitions happening in PC design as vendors introduce products optimized for Windows 8, including more thin, convertible, touch, and slate models.

Loren Loverde, Program Vice President, Worldwide Quarterly PC Trackers at IDC, says “… users are realizing that… accessing the Web, connecting to social media, sending emails, as well as using a variety of apps, doesn’t require a lot of computing power or local storage…  instead… putting a premium on… smaller devices with longer battery life, an instant-on function, and intuitive touch-centric interfaces… “

And, the report says that the commercial market has been conservative with replacements, focusing on individual systems more than large upgrade projects. In addition, workers at many companies already have portable PCs with adequate configurations. The motivation to buy a new system due to falling prices or to switch from a desktop to a portable PC is contributing less to market growth than it did in the past.

Bob O’Donnell, Program Vice President, Clients and Displays, concludes “… some of the corporate PC purchases we expected this year will no longer happen…”