of factors, including continued industry wide global product pricing pressures, increased competition, compressed product life cycles, product transitions and expected and potential increases in the cost of key components including but not limited to microprocessors, NAND flash memory, DRAM and LCDs, as well as potential increases in the costs of outside manufacturing services and a potential shift in the Company’s sales mix towards products with lower gross margins. In response to these competitive pressures, the Company expects it will continue to take product pricing actions, which would adversely affect gross margins. Gross margins could also be affected by the Company’s ability to manage product quality and warranty costs effectively and to stimulate demand for certain of its products. Due to the Company’s significant international operations, financial results can be significantly affected in the short-term by fluctuations in exchange rates. 

Research and Development Expense (“R&D”) 

R&D expense increased 34% or $449 million to $1.8 billion in 2010 compared to 2009. This increase was due primarily to an increase in headcount and related expenses in the current year to support expanded R&D activities. Also contributing to this increase in R&D expense in 2010 was the capitalization in 2009 of software development costs of $71 million related to Mac OS X Snow Leopard. Although total R&D expense increased 34% during 2010, it declined as a percentage of net sales given the 52% year-over-year increase in net sales in 2010. The Company continues to believe that focused investments in R&D are critical to its future growth and competitive position in the marketplace and are directly related to timely development of new and enhanced products that are central to the Company’s core business strategy. As such, the Company expects to make further investments in R&D to remain competitive. 

R&D expense increased 20% or $224 million to $1.3 billion in 2009 compared to 2008. This increase was due primarily to an increase in headcount in 2009 to support expanded R&D activities and higher stock-based compensation expenses. Additionally, $71 million of software development costs were capitalized related to Mac OS X Snow Leopard and excluded from R&D expense during 2009, compared to $11 million of software development costs capitalized during 2008. Although total R&D expense increased 20% during 2009, it remained relatively flat as a percentage of net sales given the 14% increase in revenue in 2009. 

Selling, General and Administrative Expense (“SG&A”) 

SG&A expense increased $1.4 billion or 33% to $5.5 billion in 2010 compared to 2009. This increase was due primarily to the Company’s continued expansion of its Retail segment, higher spending on marketing and advertising programs, increased stock-based compensation expenses and variable costs associated with the overall growth of the Company’s net sales. 

SG&A expenses increased $388 million or 10% to $4.1 billion in 2009 compared to 2008. This increase was due primarily to the Company’s continued expansion of its Retail segment in both domestic and international markets, higher stock-based