Year	Number
1960	9500
1961	9632
1962	9751
1963	9870
1964	9994
1965	10121
1966	10244
1967	10360
1968	10471
1969	10571
1970	10705
1971	10875
1972	11033
1973	11179
1974	11320
1975	11458
1976	11600
1977	11760
1978	11961
1979	12192
1980	12414
1981	12644
1982	12890
1983	13120
1984	13337
1985	13521
1986	13692
1987	13859
1988	14000
1989	14148
1990	14096
1991	13820
1992	13502
1993	13160
1994	12826
1995	12716
1996	12835
1997	12948
1998	13033
1999	13118
2000	13276
2001	13496
2002	13714
2003	13928
2004	14162
2005	14324
2006	14399
2007	14445
2008	14422
2009	14366
2010	14354
2011	14374
2012	14382
2013	14339
2014	14251
2015	14303
2016	14466
2017	14637
2018	14839
2019	15022
2020	15195
2021	15300
2022	15367
2023	15430