Apple's 10-K filing late Wednesday with the U.S. Securities and Exchange Commission revealed that the company had allotted an additional billion dollar for Research and Development spending this year.

Though R&D spend increased from $2.4 to $3.4 billion dollar, the allocation as a percentage of overall revenue remained flat at 2.2 percent despite a 45 percent increase in sales to $156 billion, The Verge has reported.

Apparently, Apple has hired more researchers and expanded its research efforts in Israel that constitutes a big chunk of the research expenditure.

Apple's headcount increased from 60,400 full-timers in 2011 to 72,800 in 2012 and the expansion of research activities in Israel is part of the increase across the board.

What's interesting to note it is that competitors' spend on R&D is much above the Cupertino giant. Google increased its R&D spend by 36 percent from 2010 to $5.2 billion in 2011.

While Microsoft increased R&D spend to $9.8 billion in 2012, eight percent above the R&D spend in 2011.

The company also increased its floor space from 13.2 to 17.3 million square feet with addition of 33 retail stores that was facilitated by 33 percent retail sales growth.

Even assets pertaining to land holdings grew from 584 acres in 2011 to 1,077 acres in 2012, as plans to open a data center in Prineville, Oregon, and addition of solar energy capacity at Maiden, North Carolina, gained ground with enhanced assets.

Reportedly, the company is also mulling expansion of its R&D operations based in its Cupertino headquarters. Apple aims to win approval for the project and have the facility built by 2015 that is likely to bring in 300,000 square foot research facility.

The Japanese sales increased 94 percent over the year with the iPhone displacing home-grown brands such as Sharp and Fujitsu-Toshiba, The Verge has pointed out.