Year	Number
1960	9446
1961	9639
1962	9851
1963	10076
1964	10318
1965	10563
1966	10813
1967	10992
1968	11079
1969	11159
1970	11366
1971	11740
1972	12172
1973	12541
1974	12662
1975	12607
1976	12539
1977	12463
1978	12387
1979	12300
1980	12252
1981	12386
1982	12666
1983	12973
1984	13299
1985	13644
1986	13985
1987	14309
1988	14632
1989	14957
1990	15293
1991	15640
1992	16004
1993	16380
1994	16770
1995	17209
1996	17732
1997	18297
1998	18852
1999	19380
2000	19726
2001	19828
2002	19851
2003	19880
2004	19907
2005	19831
2006	19619
2007	19366
2008	19102
2009	18826
2010	18540
2011	18240
2012	17946
2013	17805
2014	17796
2015	17794
2016	17816
2017	17837
2018	17864
2019	17916
2020	17972
2021	18024
2022	18055
2023	18058