Year	Number
1970	11800
1971	11500
1972	11400
1973	12000
1974	12000
1975	11800
1976	12200
1977	12300
1978	12900
1979	16800
1980	17600
1981	17000
1982	16900
1983	16600
1984	19500
1985	20300
1986	20300
1987	16600
1988	24000
1989	25800
1990	25800
1991	23000
1992	22300
1993	21800
1994	25900
1995	27200
1996	28400
1997	28400
1998	28600
1999	12000
2000	12130
2001	12306
2002	4324
2003	4912
2004	5846
2005	6255
2006	6920
2007	6918
2008	6952
2009	6804
2010	45990
2011	44126
2012	34745
2013	30612
2014	19560
2015	19395
2016	24063
2017	58880
2018	97598
2019	27035
2020	35894
2021	28642