Year	Number
1960	23553
1961	23970
1962	24290
1963	24520
1964	24644
1965	24651
1966	24550
1967	24241
1968	23758
1969	23254
1970	22713
1971	22126
1972	21594
1973	21143
1974	20693
1975	20248
1976	19695
1977	19089
1978	18607
1979	18245
1980	18010
1981	17968
1982	17978
1983	17946
1984	17905
1985	17754
1986	17468
1987	17097
1988	16779
1989	16799
1990	17453
1991	18796
1992	19726
1993	19917
1994	20057
1995	20040
1996	19972
1997	20038
1998	20227
1999	20508
2000	20721
2001	20750
2002	20654
2003	20489
2004	20269
2005	20180
2006	20307
2007	20503
2008	20707
2009	20885
2010	20819
2011	20486
2012	20154
2013	19906
2014	19730
2015	19600
2016	19477
2017	19332
2018	19147
2019	18912
2020	18494
2021	17898
2022	17287
2023	16698