Year	Number
1960	22492
1961	22968
1962	23305
1963	23596
1964	23852
1965	24074
1966	24247
1967	24342
1968	24321
1969	24178
1970	23783
1971	23123
1972	22411
1973	21742
1974	21130
1975	20584
1976	20107
1977	19695
1978	19344
1979	19059
1980	18840
1981	18675
1982	18608
1983	18675
1984	18762
1985	18825
1986	18887
1987	18919
1988	18857
1989	18776
1990	18765
1991	18796
1992	18863
1993	18937
1994	19005
1995	19006
1996	18962
1997	18873
1998	18692
1999	18456
2000	18178
2001	17798
2002	17244
2003	16680
2004	16206
2005	15753
2006	15354
2007	15023
2008	14762
2009	14562
2010	14416
2011	14363
2012	14390
2013	14435
2014	14486
2015	14538
2016	14651
2017	14815
2018	14971
2019	15109
2020	15219
2021	15294
2022	15328
2023	15319