Year	Number
1960	13012
1961	13446
1962	13848
1963	14225
1964	14607
1965	15014
1966	15433
1967	15852
1968	16253
1969	16602
1970	16932
1971	17255
1972	17531
1973	17765
1974	17952
1975	18095
1976	18250
1977	18403
1978	18509
1979	18641
1980	18871
1981	19158
1982	19400
1983	19581
1984	19726
1985	19826
1986	19911
1987	20006
1988	20154
1989	20327
1990	20614
1991	21062
1992	21526
1993	21969
1994	22363
1995	22704
1996	23003
1997	23248
1998	23464
1999	23680
2000	23868
2001	23981
2002	24019
2003	23971
2004	23830
2005	23604
2006	23312
2007	22966
2008	22575
2009	22171
2010	21997
2011	22014
2012	22056
2013	22096
2014	22087
2015	22094
2016	22112
2017	22109
2018	22039
2019	21923
2020	21826
2021	21757
2022	21677
2023	21581