Year	Number
1960	18265
1961	18601
1962	18952
1963	19319
1964	19708
1965	20156
1966	20657
1967	21187
1968	21721
1969	22176
1970	22509
1971	22593
1972	22543
1973	22488
1974	22471
1975	22676
1976	23092
1977	23636
1978	24262
1979	24902
1980	25537
1981	26279
1982	27338
1983	28613
1984	30091
1985	31718
1986	33372
1987	34891
1988	36204
1989	37397
1990	38353
1991	39175
1992	39874
1993	40343
1994	40608
1995	40739
1996	40786
1997	40820
1998	40845
1999	40773
2000	40157
2001	38688
2002	36733
2003	34816
2004	32806
2005	31133
2006	30204
2007	30036
2008	29478
2009	29207
2010	28901
2011	28872
2012	28800
2013	28416
2014	28170
2015	28551
2016	27907
2017	27425
2018	27484
2019	27130
2020	26668
2021	26416
2022	26231