Year	Number
1960	13175
1961	13489
1962	13878
1963	14281
1964	14700
1965	15101
1966	15409
1967	15756
1968	16115
1969	16484
1970	16890
1971	16935
1972	17039
1973	17159
1974	17282
1975	17388
1976	17667
1977	17931
1978	18191
1979	18448
1980	18906
1981	19151
1982	19387
1983	19649
1984	19912
1985	20164
1986	20417
1987	20648
1988	20866
1989	21065
1990	21248
1991	21133
1992	20958
1993	21045
1994	21163
1995	21300
1996	21436
1997	21568
1998	21722
1999	21832
2000	22022
2001	22258
2002	22406
2003	22550
2004	22693
2005	22863
2006	23065
2007	23267
2008	23419
2009	23521
2010	23269
2011	22952
2012	22900
2013	22823
2014	22754
2015	22710
2016	22361
2017	21946
2018	21762
2019	21564
2020	21343
2021	21093
2022	20850
2023	20625