Year	Number
1960	17054
1961	17239
1962	17419
1963	17596
1964	17759
1965	17906
1966	18080
1967	18272
1968	18459
1969	18619
1970	18780
1971	18893
1972	21967
1973	18731
1974	18503
1975	18161
1976	17707
1977	17139
1978	16487
1979	15821
1980	15129
1981	14453
1982	13846
1983	13269
1984	12730
1985	12249
1986	11808
1987	11388
1988	10995
1989	10587
1990	10146
1991	9690
1992	9203
1993	8698
1994	8187
1995	7675
1996	7189
1997	6716
1998	7343
1999	5841
2000	5465
2001	5123
2002	4817
2003	4542
2004	4293
2005	4071
2006	3876
2007	3709
2008	3559
2009	3426
2010	3301
2011	3187
2012	3077
2013	2970
2014	2867
2015	2768
2016	2671
2017	2577
2018	2483
2019	2392
2020	2303
2021	2215
2022	2127