Year	Number
1960	16210
1961	16741
1962	17287
1963	17846
1964	18399
1965	18953
1966	19476
1967	19998
1968	20504
1969	20936
1970	21300
1971	21600
1972	21839
1973	22022
1974	22223
1975	22458
1976	22671
1977	22659
1978	22452
1979	22251
1980	22050
1981	21845
1982	21627
1983	21397
1984	21183
1985	21002
1986	20859
1987	20754
1988	20684
1989	20655
1990	20661
1991	20698
1992	20755
1993	20806
1994	20843
1995	20873
1996	20871
1997	20792
1998	20684
1999	20611
2000	20582
2001	20605
2002	20677
2003	20806
2004	20967
2005	21128
2006	21265
2007	21274
2008	21158
2009	21057
2010	20997
2011	20970
2012	20857
2013	20629
2014	20415
2015	20191
2016	19955
2017	19728
2018	19477
2019	19238
2020	19086
2021	18975
2022	18924
2023	18966