Year	Number
1960	22548
1961	22893
1962	23228
1963	23590
1964	24208
1965	25019
1966	25783
1967	26556
1968	27320
1969	28045
1970	28247
1971	27864
1972	27307
1973	26641
1974	25913
1975	25149
1976	24423
1977	23796
1978	23219
1979	22710
1980	22218
1981	21664
1982	21113
1983	20611
1984	20083
1985	19625
1986	19323
1987	19075
1988	18903
1989	18833
1990	18831
1991	18838
1992	18892
1993	19048
1994	19277
1995	19561
1996	19904
1997	20248
1998	20509
1999	20675
2000	20862
2001	21023
2002	21032
2003	20972
2004	20875
2005	20722
2006	20595
2007	20520
2008	20497
2009	20504
2010	20377
2011	20134
2012	19861
2013	19579
2014	19326
2015	19029
2016	18688
2017	18398
2018	18118
2019	17859
2020	17683
2021	17545
2022	17390
2023	17149