Year	Number
1960	15556
1961	15895
1962	16242
1963	16583
1964	16926
1965	17273
1966	17588
1967	17907
1968	18291
1969	18403
1970	18169
1971	18212
1972	18575
1973	19010
1974	19439
1975	19803
1976	20160
1977	20482
1978	20795
1979	21087
1980	21346
1981	21596
1982	21804
1983	21973
1984	22096
1985	22241
1986	22390
1987	22437
1988	22542
1989	22803
1990	23132
1991	23459
1992	23808
1993	24181
1994	24535
1995	24886
1996	25235
1997	25596
1998	25997
1999	26404
2000	26823
2001	27335
2002	27969
2003	28601
2004	29093
2005	29508
2006	29959
2007	30372
2008	30700
2009	31059
2010	31608
2011	32495
2012	33132
2013	33285
2014	33389
2015	33570
2016	33834
2017	34056
2018	34156
2019	34178
2020	34007
2021	33745
2022	33660
2023	33642