Year	Number
1980	18118
1981	19087
1982	17015
1983	15103
1984	14301
1985	10632
1986	10653
1987	11432
1988	10001
1989	11275
1990	13827
1991	14346
1992	17240
1993	18712
1994	21619
1995	16916
1996	22305
1997	36674
1998	34477
1999	38749
2000	42448
2001	38249
2002	37345
2003	35788
2004	37364
2005	42138
2006	46661
2007	49769
2008	51585
2009	44029
2010	46470
2011	50661
2012	54008
2013	53989
2014	55279
2015	55995
2016	50243
2017	48021