Year	Number
1960	20307
1961	20897
1962	21424
1963	21896
1964	22285
1965	22605
1966	22915
1967	23206
1968	23470
1969	23705
1970	23893
1971	24024
1972	24089
1973	24087
1974	24012
1975	23847
1976	23629
1977	23406
1978	23200
1979	23014
1980	22827
1981	22563
1982	22241
1983	21959
1984	21729
1985	21542
1986	21373
1987	21206
1988	21029
1989	20831
1990	20613
1991	20361
1992	20103
1993	19864
1994	19625
1995	19365
1996	19058
1997	18708
1998	18336
1999	17968
2000	17634
2001	17340
2002	17043
2003	16708
2004	16339
2005	15945
2006	15511
2007	15050
2008	14608
2009	14198
2010	13808
2011	13442
2012	13121
2013	12838
2014	12592
2015	12377
2016	12158
2017	11955
2018	11780
2019	11611
2020	11468
2021	11341
2022	11216
2023	11077