Year	Number
1960	21367
1961	21092
1962	20957
1963	20889
1964	20836
1965	20796
1966	20779
1967	20752
1968	20669
1969	20527
1970	20311
1971	20027
1972	19745
1973	19526
1974	19331
1975	19154
1976	18977
1977	18747
1978	18459
1979	18120
1980	17735
1981	17303
1982	16867
1983	16462
1984	16132
1985	15825
1986	15612
1987	15348
1988	14933
1989	14457
1990	13991
1991	13589
1992	13268
1993	13026
1994	12836
1995	12610
1996	12279
1997	11866
1998	11423
1999	11014
2000	10653
2001	10372
2002	10158
2003	9933
2004	9663
2005	9399
2006	9154
2007	8943
2008	8805
2009	8753
2010	8766
2011	8814
2012	8894
2013	9023
2014	9181
2015	9713
2016	12363
2017	12203
2018	11779
2019	10977
2020	10160
2021	9684
2022	9392