Year	Number
1970	9700
1971	19800
1972	20600
1973	20000
1974	19700
1975	8400
1976	9200
1977	10100
1978	19100
1979	18900
1980	18500
1981	19200
1982	18500
1983	18500
1984	21100
1985	22500
1986	22700
1987	21800
1988	27800
1989	29600
1990	29500
1991	29900
1992	39100
1993	41900
1994	44200
1995	48000
1996	50000
1997	51400
1998	50100
1999	51600
2000	56427
2001	47648
2002	49404
2003	46334
2004	34152
2005	34104
2006	36257
2007	47038
2008	45309
2009	47856
2010	47829
2011	47195
2012	47073.827458256
2013	46644
2014	49177
2015	49020
2016	50548
2017	50330
2018	53901
2019	49276
2020	12221
2021	23090