Year	Number
1980	3501
1981	3466
1983	3994
1984	4451
1998	10778
1999	12276
2000	17429
2001	13427
2002	11497
2003	12147
2004	14089
2005	15451
2006	16021
2007	17558
2008	12866
2009	10495
2010	12595
2011	13960
2012	14657
2013	15229
2014	15655
2015	15987
2016	16896
2017	17569