Year	Number
1960	25329
1961	25672
1962	26075
1963	26478
1964	26835
1965	27153
1966	27320
1967	27480
1968	27747
1969	27993
1970	28148
1971	28314
1972	27902
1973	27152
1974	26745
1975	26184
1976	25529
1977	24856
1978	24021
1979	23337
1980	22813
1981	22407
1982	22179
1983	21937
1984	21730
1985	21605
1986	21446
1987	21179
1988	20807
1989	20454
1990	20229
1991	20080
1992	19987
1993	19971
1994	19896
1995	19812
1996	19782
1997	19642
1998	19052
1999	18112
2000	17103
2001	16206
2002	15932
2003	15944
2004	15885
2005	15946
2006	16054
2007	16147
2008	16154
2009	16064
2010	16071
2011	16095
2012	16027
2013	16026
2014	16062
2015	16066
2016	15953
2017	15620
2018	14523
2019	13730
2020	13448
2021	12991
2022	12602
2023	12272