Year	Number
1980	8582
1981	9891
1982	10008
1983	8290
1984	9206
1986	8659
1987	10583
1988	10457
1989	9661
1990	10873
1991	10600
1992	10991
1993	14179
1994	14063
1995	17087
1996	18504
1997	20336
1998	23600
1999	23938
2000	25678
2001	21901
2002	20367
2003	22768
2004	23826
2005	27835
2006	31795
2007	35001
2008	29907
2009	26621
2010	30549
2011	33484
2012	34604
2013	36070
2014	35418
2015	36973
2016	37976
2017	26251