Travel and tourism contributed 17.5 per cent of Tanzania's gross domestic product in 2016 and employed 11.0 per cent of the country's labour force (1,189,300 jobs) in 2013. Overall receipts rose from US$1.74 billion in 2004 to US$4.48 billion in 2013, and receipts from international tourists rose from US$1.255 billion in 2010 to US$2 billion in 2016. In 2016, 1,284,279 tourists arrived at Tanzania's borders compared to 590,000 in 2005. The vast majority of tourists visit Zanzibar or a "northern circuit" of Serengeti National Park, the Ngorongoro Conservation Area, Tarangire National Park, Lake Manyara National Park, and Mount Kilimanjaro. In 2013, the most visited national park was Serengeti (452,485 tourists), followed by Manyara (187,773) and Tarangire (165,949).