Year	Number
1970	10500
1971	10000
1972	9600
1973	11500
1974	9000
1975	13700
1976	14900
1977	4100
1978	8900
1979	13000
1980	17500
1981	18700
1982	13400
1983	11800
1984	10400
1985	13800
1986	11200
1987	12300
1988	12100
1989	8000
1990	7500
1991	9400
1992	7500
1993	5700
1994	5400
1995	5600
1996	6100
1997	6000
1998	6100
1999	5000
2000	5973
2001	4360
2002	4401
2003	6082
2004	6441
2005	6062
2006	5068
2007	5457
2008	5460
2009	21088
2010	21825
2011	26332.300586101
2012	28130.4720729721
2013	27625.772
2014	31106.181
2015	35374
2016	27422
2017	47741
2018	90017
2019	91864
2020	42693
2021	54741