23.14% of web site visits in December 2012 came from mobile devices, an 84% increase over December 2011 and a 283% increase over January 2011, finds a study of two million unique web visits across various industries by marketing and public relations firm Walker Sands Communications.

“Mobile traffic is increasing at a significant rate each year. In January 2011 we found mobile traffic accounted for only 6% of total web site visits. Now, nearly two years later, mobile accounts for nearly a quarter of all web site visits,” says John Fairley, director of web services and social media at Walker Sands. “Mobile is no longer an option, but a necessity. Companies must develop a user-friendly mobile site to keep pace with traffic that consistently doubles year over year.”

Traffic from smartphones and tablets accounted for 12.59% of total traffic in Q4 2011, 13.41% in Q1 2012, 16.63% in Q2 2012, 17.53% in Q3 2012 and 23.14% in Q4 2012, Walker Sands says.

The study also examined web traffic by operating system and device, finding Apple Inc.’s iOS holds a majority of mobile traffic at 52%, with Android at 43% of traffic. Apple iOS devices led Android in mobile traffic by only 1% at the end of 2011, the study says.

“This Apple iOS mobile traffic surge happened much in thanks to the releases of the iPhone 5 in late September and iPad mini in late October,” says Daniel LaLoggia, digital marketing manager at Walker Sands. “Android’s share slipped a little, but its big surge came in the beginning of 2012 with its latest device release. Blackberry, driving only 2% of total mobile traffic, is nearly irrelevant now.”

Breaking down Apple traffic, 35% of mobile traffic stemmed from iPhones and 17% from iPad and iPad mini tablets, the study says. Walker Sands did not break out numbers for Android smartphones versus Android tablets, but other studies have shown that web traffic from iPad tablets dwarfs traffic from Android tablets.

“The main takeaway is that businesses must be conscious that there are now four possible screen sizes from which users will view their site—desktops, full tablets, smaller tablets and smartphones,” Fairley adds. “A site design that renders correctly on each device is crucial for success in developing a mobile presence.”