| Country | 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2015 | 2016 | 2017 |
|---|
| Gabon | 6,500 | 6,300 | 5,500 | 5,700 | 5,500 | 5,900 | 7,000 | 7,100 | 14,000 | 14,200 | 13,900 | 14,500 | 16,400 | 16,800 | 19,200 | 18,600 | 19,300 | 18,100 | | Poland | 7,200 | 8,500 | | 9,500 | 11,100 | 12,000 | 13,100 | 14,300 | 16,200 | 17,300 | 17,900 | 18,800 | 20,600 | 20,900 | 21,100 | 26,500 | 27,700 | 29,600 | | Sweden | 20,700 | 22,200 | | 25,400 | 26,800 | 28,400 | 29,800 | 32,200 | 37,500 | 38,100 | 37,000 | 39,100 | 40,900 | 41,900 | 40,900 | 47,900 | 49,700 | 51,200 | | United Kingdom | 21,800 | 22,800 | | 25,300 | 27,700 | 29,600 | 30,100 | 31,800 | 35,000 | 36,500 | 34,200 | 34,800 | 36,600 | 37,500 | 37,300 | 41,200 | 42,500 | 44,300 | | United States | 33,900 | 36,200 | 36,300 | 37,600 | 37,800 | 40,100 | 41,600 | 44,000 | 45,800 | 46,900 | 46,000 | 47,200 | 49,000 | 50,700 | 52,800 | 55,800 | 57,300 | 59,800 |
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