net sales. The increase in gross margin was partially offset by the impact of a stronger U.S. dollar. The gross margin percentage during the first half of 2012 was 45.9% compared to 41.4% during the second half of 2012. The primary drivers of higher gross margin in the first half of 2012 compared to the second half are a higher mix of iPhone sales and improved leverage on fixed costs from higher net sales. Additionally, gross margin in the second half of 2012 was also affected by the introduction of new products with flat pricing that have higher cost structures and deliver greater value to customers, price reductions on certain existing products, higher transition costs associated with product launches, and continued strengthening of the U.S. dollar; partially offset by lower commodity costs. 

The Company anticipates gross margin during the first quarter of 2014 to be between 36.5% and 37.5%. The foregoing statement regarding the Company’s expected gross margin percentage in the first quarter of 2014 is forward-looking and could differ from actual results. The Company’s future gross margin can be impacted by multiple factors including, but not limited to those set forth above in Part I, Item 1A of this Form 10-K under the heading “Risk Factors” and those described in this paragraph. In general, gross margins and margins on individual products will remain under downward pressure due to a variety of factors, including continued industry wide global product pricing pressures, increased competition, compressed product life cycles, product transitions, potential increases in the cost of components, and potential strengthening of the U.S. dollar, 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 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. 

The growth in R&D expense was driven by an increase in headcount and related expenses to support expanded R&D activities. Although total R&D expense increased 32% and 39% in 2013 and 2012, respectively, it remained fairly consistent as a percentage of net sales. 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. 

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

The growth in SG&A during 2013 was primarily due to the Company’s continued expansion of its Retail segment and increased headcount and related expenses, partially offset by decreased