Year	Number
1960	6106
1961	6118
1962	6314
1963	7229
1964	7454
1965	8004
1966	8533
1967	9055
1968	10205
1969	10914
1970	11520
1971	13130
1972	14354
1973	15955
1974	17089
1975	17981
1976	18342
1977	17724
1978	18013
1979	17661
1980	17824
1981	17415
1982	17050
1983	16750
1984	16462
1985	16135
1986	15802
1987	15516
1988	15319
1989	15220
1990	15598
1991	15747
1992	15959
1993	16149
1994	16273
1995	16112
1996	15747
1997	15403
1998	15017
1999	14586
2000	14237
2001	13916
2002	13541
2003	13150
2004	12752
2005	12356
2006	11967
2007	11635
2008	11367
2009	11164
2010	10978
2011	10778
2012	10599
2013	10457
2014	10362
2015	10303
2016	10263
2017	10231
2018	10195
2019	10138
2020	10100
2021	10048
2022	9965
2023	9863