birth rate is also double the national average. Some 10% of the population are foreign-born (extranjeros), with those from Latin American countries representing over half of these, and those from other European countries a further 33%. Again, many of the immigrant population are professionals employed by multinational companies in fields such as technology, who have settled in Spain after first arriving on work assignment, many of whom are married to Spanish nationals. Educational accreditation among Tres Cantos inhabitants is also above the national average, with some 60% of prime income earners holding a tertiary qualification or higher. Average income levels reflect these education levels and professional employment opportunities, with over 55% having salaries in the upper-middle or higher income range. Many households have dual-incomes. Approximately 15% of households are classified as lower-middle and low-income households. An overwhelming majority of the employed work in the services sector, either in Madrid or in Tres Cantos itself. A majority of working residents regularly commute to Madrid for work, with only about a quarter of the workforce having employment in Tres Cantos itself. Those who remain behind are joined by a daily influx of approximately 20,000 who commute from Madrid and its environs to Tres Cantos for work. Light and medium industries account for some 20% of employment in Tres Cantos, the construction sector providing a further 7.4%; a bare handful (0.2%) are employed in agriculture. Economy and industry Tres Cantos' main economic activity is derived from the existence of various high-tech factories and headquarters in designated zones, including from the pharmaceutical, aerospace and computing industries. A production hub of Netflix is also found here. Approximately 20,000 employees from outside of Tres Cantos (predominantly Madrid) commute daily to work in its industrial zones its "Technological Park," home of cutting-edge companies in the aerospace industry, such as GMV Innovating Solutions. Other multinational corporations with offices and/or production in Tres Cantos are: Lucent Technologies, BP Solar, BDF Nivea, Nokia Siemens Networks, Samsonite, Altair, Hella, Siemens, Dannon, GMV, IFS. The once largest cable provider in Spain, SOGECABLE, relocated here. The headquarters of both the Real Automóvil Club de España and the (CEM) are located in Tres Cantos. Sister cities Tres Cantos is a sister city to the planned cities of Columbia, Maryland, United States, Cergy-Pontoise, France and Nejapa, El Salvador. Transport system Tres Cantos has variety of transport connections. Train transit connects Tres Cantos with the district