Year	Number
1960	18494
1961	18821
1962	19204
1963	19634
1964	20052
1965	20472
1966	20913
1967	21353
1968	21773
1969	22138
1970	22478
1971	22815
1972	23057
1973	23277
1974	23383
1975	23415
1976	23458
1977	23950
1978	24149
1979	24565
1980	24898
1981	25102
1982	25285
1983	25421
1984	25512
1985	25454
1986	25387
1987	25220
1988	25301
1989	26447
1990	26982
1991	27501
1992	27991
1993	28392
1994	28688
1995	29300
1996	29606
1997	30077
1998	30626
1999	30921
2000	31144
2001	31131
2002	31041
2003	30981
2004	30698
2005	30461
2006	30173
2007	29872
2008	29611
2009	29352
2010	29194
2011	28974
2012	28503
2013	28123
2014	27789
2015	27774
2016	27735
2017	27914
2018	27489
2019	27352
2020	27281
2021	27218
2022	27025