minibuses, particularly in Kigali, operate an unscheduled service, under a shared taxi system, while others run to a schedule, offering express routes between the major cities. There are a smaller number of large buses, which operate a scheduled service around the country. The principal private hire vehicle is the motorcycle taxi; in 2013 there were 9,609 registered motorcycle taxis in Rwanda, compared with just 579 taxicabs. Coach services are available to various destinations in neighbouring countries. The country has an international airport at Kigali that serves several international destinations, the busiest routes being those to Nairobi and Entebbe; there is one domestic route, between Kigali and Kamembe Airport near Cyangugu. In 2017, construction began on the Bugesera International Airport, to the south of Kigali, which will become the country's largest when it opens, complementing the existing Kigali airport. The national carrier is RwandAir, and the country is served by seven foreign airlines. the country has no railways, but there is a project underway, in conjunction with Burundi and Tanzania, to extend the Tanzanian Central Line into Rwanda; the three countries have invited expressions of interest from private firms to form a public private partnership for the scheme. There is no public water transport between the port cities on Lake Kivu, although a limited private service exists and the government has initiated a programme to develop a full service. The Ministry of Infrastructure is also investigating the feasibility of linking Rwanda to Lake Victoria via shipping on the Akagera River. Demographics , the National Institute of Statistics of Rwanda estimated Rwanda's population to be 11,262,564, while the projection for 2021 was 12,955,736. The 2012 census recorded a population of 10,515,973. The population is young: in the 2012 census, 43.3% of the population were aged 15 and under, and 53.4% were between 16 and 64. According to the CIA World Factbook, the annual birth rate is estimated at 40.2 births per 1,000 inhabitants in 2015, and the death rate at 14.9. The life expectancy is 67.67 years (69.27 years for females and 67.11 years for males), which is the 26th lowest out of 224 countries and territories. The overall sex ratio of the country is 95.9 males per 100 females. At , Rwanda's population density is amongst the highest in Africa. Historians such as Gérard Prunier believe that the 1994 genocide can be partly attributed to the population density. The population is