Year	Number
1973	15500
1974	17600
1975	17800
1976	17600
1977	12800
1978	13200
1979	15200
1980	21200
1981	19200
1982	15500
1983	15500
1984	15700
1985	15800
1986	14200
1987	13100
1988	23700
1989	23600
1990	23500
1991	23200
1992	27200
1993	27000
1994	31000
1995	32600
1996	33600
1997	86900
1998	87900
1999	57300
2000	57776
2001	62768
2002	37685
2003	38732
2004	36920
2005	41886
2006	46866
2007	46359
2008	46467
2009	45595
2010	26127
2011	18142
2012	16011.2858124356
2013	11748
2014	19140
2015	19487
2016	20906
2017	21855
2018	24134
2019	25859
2020	10450
2021	5791