Year	Number
1960	13981
1961	14412
1962	14877
1963	15373
1964	15904
1965	16426
1966	16831
1967	17252
1968	17669
1969	18084
1970	18505
1971	18427
1972	18330
1973	18257
1974	18192
1975	18133
1976	18279
1977	18423
1978	18565
1979	18698
1980	19064
1981	19267
1982	19485
1983	19738
1984	19982
1985	20220
1986	20469
1987	20705
1988	20931
1989	21126
1990	21283
1991	21115
1992	20876
1993	20901
1994	20972
1995	21059
1996	21127
1997	21186
1998	21295
1999	21382
2000	21545
2001	21752
2002	21879
2003	22020
2004	22170
2005	22331
2006	22495
2007	22638
2008	22753
2009	22858
2010	22617
2011	22308
2012	22280
2013	22273
2014	22269
2015	22247
2016	21896
2017	21470
2018	21267
2019	21061
2020	20857
2021	20621
2022	20414
2023	20275