Year	Number
1960	9833
1961	10015
1962	10247
1963	10516
1964	10820
1965	11151
1966	11483
1967	11808
1968	12140
1969	12473
1970	12698
1971	12796
1972	12869
1973	12946
1974	13036
1975	13154
1976	13276
1977	13364
1978	13431
1979	13495
1980	13673
1981	14020
1982	14433
1983	14867
1984	15333
1985	15840
1986	16394
1987	16999
1988	17657
1989	18370
1990	19014
1991	19517
1992	19979
1993	20450
1994	20936
1995	21431
1996	21921
1997	22384
1998	22803
1999	23198
2000	23382
2001	23242
2002	22951
2003	22597
2004	22173
2005	21676
2006	21125
2007	20545
2008	19978
2009	19480
2010	18964
2011	18394
2012	17846
2013	17302
2014	16750
2015	16180
2016	15585
2017	14966
2018	14326
2019	13672
2020	13025
2021	12390
2022	12019
2023	11880