Year	Number
1980	15535
1981	16225
1982	15782
1983	17157
1984	18804
1985	24744
1986	27251
1987	31241
1988	39479
1989	39691
1990	36633
1991	34154
1992	33159
1993	31789
1994	34072
1995	37518
1996	33674
1997	34554
1998	35835
1999	37373
2000	45474
2001	42130
2002	39885
2003	40624
2004	44210
2005	43410
2006	44162
2007	45962
2008	42872
2009	40409
2010	41833
2011	42360
2012	39569
2013	40622
2014	40195
2015	39774
2016	41861
2017	41911