Year	Number
1960	22245
1961	22695
1962	22995
1963	23236
1964	23429
1965	23573
1966	23664
1967	23679
1968	23587
1969	23381
1970	22947
1971	22275
1972	21556
1973	20880
1974	20265
1975	19726
1976	19267
1977	18877
1978	18544
1979	18259
1980	17996
1981	17778
1982	17688
1983	17747
1984	17838
1985	17915
1986	17989
1987	18024
1988	17965
1989	17887
1990	17881
1991	17958
1992	18105
1993	18257
1994	18395
1995	18453
1996	18440
1997	18362
1998	18175
1999	17903
2000	17568
2001	17137
2002	16562
2003	15998
2004	15528
2005	15086
2006	14700
2007	14379
2008	14127
2009	13938
2010	13799
2011	13752
2012	13786
2013	13841
2014	13907
2015	13974
2016	14089
2017	14245
2018	14390
2019	14519
2020	14625
2021	14701
2022	14739
2023	14736