by higher product cost structures and, to a lesser extent, by the effect of weakness in most foreign currencies relative to the U.S. dollar. 

The year-over-year increase in the gross margin percentage in 2014 was driven by multiple factors including lower commodity costs, a favorable shift in mix to products with higher margins and improved leverage on fixed costs from higher net sales, which was partially offset by the weakness in several foreign currencies relative to the U.S. dollar, price reductions on select products and higher cost structures on certain new products. 

The Company anticipates gross margin during the first quarter of 2016 to be between 39% and 40%. The foregoing statement regarding the Company’s expected gross margin percentage in the first quarter of 2016 is forward-looking and could differ from actual results. The Company’s future gross margins can be impacted by multiple factors including, but not limited to, those set forth in Part I, Item 1A of this Form 10-K under the heading “Risk Factors” and those described in this paragraph. In general, the Company believes gross margins 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, its financial condition and operating results, including gross margins, could be significantly affected by fluctuations in exchange rates. 

The year-over-year growth in R&D expense in 2015 and 2014 was driven primarily by an increase in headcount and related expenses, including share-based compensation costs, and material costs to support expanded R&D activities. 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 updated products that are central to the Company’s core business strategy. 

Selling, General and Administrative 

The year-over-year growth in selling, general and administrative expense in 2015 and 2014 was primarily due to increased headcount and related expenses, including share-based compensation costs, and higher spending on marketing and advertising. 

The increase in other income/(expense), net during 2015 compared to 2014 was due primarily to higher interest income, partially offset by higher expenses associated with foreign exchange activity and higher interest expense on debt. The decrease in other income and expense during 2014