Year	Number
1976	1500
1977	1500
1978	1500
1979	1500
1980	1600
1981	2400
1982	4800
1983	7300
1984	7600
1985	8100
1986	6100
1987	6700
1988	6700
1989	6700
1990	6700
1991	6600
1992	6800
1993	6800
1994	6800
1995	7100
1996	7400
1997	14600
1998	14800
1999	12100
2000	13010
2001	8745
2002	8735
2003	9434
2004	16612
2005	19905
2006	19862
2007	21086
2008	12236
2009	11560
2010	10363
2011	10658.0712931195
2012	10555.2286515647
2013	8148
2014	7728
2015	7989
2016	8745
2017	4868
2018	9385
2019	10205
2020	4248
2021	1625.248