parties that are in close proximity to our Adams plant and could supply small quantities of lime to certain of our PCC satellite facilities  that are in close geographic proximity to the Adams plant. Carbon dioxide is readily available in exhaust gas from the host paper mills,  or other operations at our merchant facilities.  The principal raw materials used in the Company's monolithic refractory products are refractory-grade magnesia and various forms  of alumina silicates. Approximately 45%  percent of the Company’s  magnesia requirements were purchased from sources in China  over the past five years. The price and availability of bulk raw materials from China are subject to fluctuations that could affect the  Company's sales to its customers. In addition, the volatility of transportation costs has also affected the delivered cost of raw materials  imported from China to North America and Europe. The Company has developed alternate sources of magnesia over the past few  years that have reduced our reliance on China sourced magnesia. Presently, we procure the majority of our magnesia requirements  from other locations, including Brazil, Turkey, United States, Netherlands, Russia and Japan. The amount sourced from China and  other locations can vary from year to year depending upon price and availability from each source. The alumina we utilize in our  business is readily available from numerous sources. The Company also purchases calcium metal, calcium silicide, graphite, calcium  carbide and various alloys for use in the production of metallurgical wire products and uses lime and aluminum in the production of  calcium metal.  The Company is continually engaged in efforts to develop new products and technologies and refine existing products and  technologies in order to remain competitive and to position itself as a market leader.  With respect to its PCC products, the Company competes for sales to the paper industry with other minerals, such as GCC and  kaolin, based in large part upon technological know-how, patents and processes that allow the Company to deliver PCC that it believes  imparts gloss, brightness, opacity and other properties to paper on an economical basis. The Company is the leading manufacturer and  supplier of PCC to the paper industry. The Company competes in sales of its limestone and talc based primarily upon quality, price, and geographic location. With respect to the Company's refractory products, competitive conditions vary by geographic region. Competition is based upon  the performance characteristics of the product (including strength, consistency and ease of application), price, and the availability of  technical support. Many of the Company's product lines are technologically advanced. Our expertise in inorganic chemistry, crystallography and  structural analysis, fine particle technology and other aspects of materials science apply to and support all of our product lines. The  Company's business strategy for growth in sales and profitability depends, to a large extent, on the continued success of its research  and development activities. Among the significant achievements of the Company's research and development efforts have been: the  satellite PCC plant concept; PCC crystal morphologies for paper coating; AT$^{®}$ PCC for wood-containing papers; FulFill® high filler  technology systems; the development of FASTFIRE$^{®}$ and OPTIFORM$^{®}$ shotcrete refractory products; LACAM$^{®}$ laser-based  refractory measurement systems; the MINSCAN$^{®}$ and HOTCRETE$^{®}$ application systems; and EMforce$^{®}$, Optibloc$^{®}$ and Titanium  Dioxide (TiO2) extenders for the Processed Minerals and Specialty PCC product lines.  Under the FulFill® platform of products, the Company continues to develop its filler-fiber composite material. The FulFill® brand  High Filler Technology is a portfolio of high-filler technologies that offers papermakers a variety of efficient, flexible solutions that  decreases dependency on natural fiber and reduces costs. The FulFill® E-325 series allows papermakers to increase filler loading  levels of precipitated calcium carbonate (PCC), which replaces higher cost pulp, and increases PCC usage. Depending on paper  grades, this PCC volume increase may range from 15 to 30 percent. The Company continues to progress in the commercialization of  FulFill® E-325. We have signed agreements with fifteen paper mills and are actively engaged with additional paper mill sites for  further FulFill® deployment. We continue product development with other products within this platform. The Company will also continue to reformulate its refractory materials to be more competitive, and will also continue development  of unique calcium carbonates for use in novel biopolymers.  For the years ended December 31, 2013, 2012 and 2011, the Company spent approximately $20.1 million, $20.2 million and $19.3  million, respectively, on research and development. The Company's research and development spending for 2013, 2012 and 2011 was  approximately 2.0%, 2.0% and 1.9% of net sales, respectively.  The Company maintains its primary research facilities in Bethlehem and Easton, Pennsylvania. It also has research and  development facilities in China, Germany, Ireland, Japan and Turkey. Approximately 71 employees worldwide are engaged in  research and development. In addition, the Company has access to some of the world's most advanced papermaking and paper coating  pilot facilities.  7  Competition Research and Development