Year	Number
1980	15219
1981	16862
1982	16402
1983	17456
1984	20044
1985	21472
1986	21250
1987	19267
1988	24834
1989	26284
1990	25681
1991	23513
1992	23875
1993	24937
1994	27730
1995	28704
1996	33341
1997	32756
1998	35390
1999	40365
2000	46252
2001	39092
2002	36732
2003	38712
2004	39888
2005	41832
2006	45031
2007	47758
2008	45619
2009	40956
2010	45220
2011	48472
2012	50110
2013	49819
2014	51028
2015	52461
2016	54665
2017	58913