Year	Number
1960	20996
1961	21597
1962	22127
1963	22595
1964	22989
1965	23327
1966	23653
1967	23959
1968	24238
1969	24484
1970	24681
1971	24816
1972	24882
1973	24875
1974	24792
1975	24620
1976	24391
1977	24162
1978	23952
1979	23760
1980	23564
1981	23299
1982	22988
1983	22716
1984	22493
1985	22317
1986	22169
1987	22032
1988	21892
1989	21746
1990	21572
1991	21319
1992	21018
1993	20730
1994	20451
1995	20159
1996	19826
1997	19464
1998	19083
1999	18699
2000	18339
2001	18009
2002	17679
2003	17314
2004	16910
2005	16489
2006	16042
2007	15574
2008	15128
2009	14709
2010	14312
2011	13935
2012	13598
2013	13300
2014	13039
2015	12805
2016	12569
2017	12357
2018	12173
2019	11995
2020	11843
2021	11708
2022	11575
2023	11428