Sales Cost of Sales ADTRAN 2013 Annual Report 24 Carrier Networks cost of sales increased from 49.7% of sales in 2012 to 53.4% of sales in 2013. The increase in Carrier  Networks cost of sales as a percentage of sales was primarily attributable to a higher volume of the lower gross margin products related to the acquired broadband access business, customer price movements to achieve market share position and shifts in customer mix. As a percentage of sales, cost of sales increased from 49.0% in 2012 to 51.9% in 2013. The increase was primarily attributable to a higher volume of the lower gross margin products related to the broadband access business we acquired in 2012, customer price movements to achieve market share position and shifts in customer mix. Loop Access product sales decreased $26.6 million in 2013 compared to 2012 primarily due to a $25.3 million decrease in  HDSL product sales, which is further discussed above. Business Networking product sales increased $19.6 million in 2013 compared to 2012 primarily due to a $21.5 million  increase in Internetworking product sales across both divisions, partially offset by a $1.9 million decrease in legacy product  sales. The increase in sales of our Internetworking products was primarily attributable to an improved spending environment  and reflected an increase in sales to both carriers and value added resellers. The decrease in legacy products was expected and  is further discussed above. Carrier Systems product sales increased $28.2 million in 2013 compared to 2012 primarily due to a $20.5 million increase in Broadband Access product sales, a $3.9 million increase in Optical product sales, and a $3.9 million increase in  legacy product sales. The increase in Carrier Systems product sales is primarily attributable to the factors discussed above.  International sales, which are included in the Carrier Networks and Enterprise Networks amounts discussed above, increased 23.6% from $150.2 million in 2012 to $185.7 million in 2013. International sales, as a percentage of total sales, increased from 24.2% in 2012 to 28.9% in 2013. The increase in international sales is primarily attributable to an increase in  sales in the EMEA region, partially offset by a decrease in sales in Latin America and the Asia-Pacific region. Enterprise Networks sales increased 9.7% from $128.5 million in 2012 to $141.0 million in 2013. The increase is attribut- able to an increase in sales of our Internetworking products, partially offset by decreases in sales of our legacy products. The  increase in sales of our Internetworking products is primarily attributable to an improved spending environment and reflected  an increase in sales of Ethernet switches and IP business gateways to both carriers and value added resellers. The decrease  in legacy products was expected and is discussed further above. Internetworking product sales attributable to Enterprise  Networks were 93.6% of the division’s sales in 2013 compared with 91.5% in 2012. Legacy products primarily comprise the  remainder of Enterprise Networks sales. Enterprise Networks sales as a percentage of total sales increased from 20.7% in 2012 to 22.0% in 2013. Carrier Networks sales increased 1.8% from $492.1 million in 2012 to $500.7 million in 2013. The increase in sales is  primarily attributable to increases in sales of Broadband Access products, Internetworking products, and Optical products,  partially offset by a decrease in sales of our HDSL products. The increase in sales of our Broadband Access products is primarily attributable to initial VDSL2 vectoring technology shipments to Europe, partially offset by fluctuations in project  installation activities at a Latin American carrier. The increase in sales of our Internetworking products is primarily attribut- able to an improved spending environment and increases in EFM NTE sales and FTTP ONT sales to carriers. The increase  in sales of our Optical products is primarily attributable to a technology shift from Time Division Multiplexed (TDM) and  SONET/SDH architectures to Ethernet-based packet networks. We offer Ethernet-based solutions within our Optical products  that address this technology change, and we expect sales of our Optical products will increase over time due to this transition.  The decrease in sales of HDSL and other legacy products has been expected as customers continue to upgrade their networks  to deliver higher bandwidth services by migrating to newer technologies, including to our core products from our Broadband  Access, Internetworking and Optical product lines. While we expect that revenues from HDSL and our other legacy products  will continue to decline over time, these revenues may continue for years because of the time required for our customers to  transition to newer technologies. Our sales increased 3.4% from $620.6 million in 2012 to $641.7 million in 2013. The increase in sales is primarily attributable  to a $21.5 million increase in sales of our Internetworking products, a $20.5 million increase in sales of our Broadband Access  products, a $3.9 million increase in sales of our Optical products, partially offset by a $24.7 million decrease in sales of our  HDSL and other legacy products. 2013 Compared to 2012