Year	Number
1970	6600
1971	6600
1972	6900
1973	8400
1974	13600
1975	13200
1976	15900
1977	22000
1978	17900
1979	18100
1980	18200
1981	12500
1982	17100
1983	18700
1984	22100
1985	23000
1986	24600
1987	23700
1988	23000
1989	24100
1990	22000
1991	20200
1992	16100
1993	18100
1994	21300
1995	22200
1996	17100
1997	25600
1998	15400
1999	17900
2000	23298
2001	20781
2002	17748
2003	26844
2004	30524
2005	38995
2006	42754
2007	51222
2008	55386
2009	57893
2010	61515
2011	57823
2012	51685
2013	43956
2014	42249.8
2015	45596
2016	46733
2017	52063
2018	55637
2019	58509
2020	22125
2021	30789