Year	Number
1960	20860
1961	21079
1962	21282
1963	21415
1964	21620
1965	22037
1966	22443
1967	22855
1968	23296
1969	23712
1970	24002
1971	24335
1972	24372
1973	24361
1974	24394
1975	24515
1976	24729
1977	24886
1978	25182
1979	25494
1980	25748
1981	26202
1982	26465
1983	26652
1984	27046
1985	27311
1986	27566
1987	27755
1988	27681
1989	27618
1990	27513
1991	27585
1992	27731
1993	28008
1994	28416
1995	29010
1996	29494
1997	29954
1998	30624
1999	30937
2000	31372
2001	31759
2002	31774
2003	31576
2004	31543
2005	31665
2006	31878
2007	32218
2008	32390
2009	32344
2010	32197
2011	32043
2012	32001
2013	31831
2014	31742
2015	31990
2016	31898
2017	31632
2018	31345
2019	30844
2020	30523
2021	30383
2022	30347