Year	Number
1970	6200
1971	6600
1972	7400
1973	8400
1974	8800
1975	9500
1976	9800
1977	11100
1978	11100
1979	11600
1980	12200
1981	13400
1982	14900
1983	16500
1984	16700
1985	16600
1986	15400
1987	14400
1988	16400
1989	17000
1990	18200
1991	19000
1992	14400
1993	9100
1994	7100
1995	5800
1996	6100
1997	6000
1998	6000
1999	6100
2000	6194
2001	5884
2002	5884
2003	6414
2004	8042
2005	13335
2006	12657
2007	13477
2008	9930
2009	9812
2010	34878.0771737788
2011	27770.5020633663
2012	16514.4315772057
2013	32064
2014	26414
2015	13298
2016	10764
2017	9686
2018	12340
2019	11339
2020	6032.238
2021	9046.238