Year	Number
1970	15683
1971	16257
1972	16819
1973	17396
1974	17892
1975	18296
1976	18542
1977	18787
1978	19146
1979	19570
1980	20134
1981	20749
1982	21339
1983	22007
1984	22843
1985	23518
1986	23999
1987	24537
1988	24797
1989	25080
1990	25447
1991	25654
1992	25831
1993	26028
1994	26144
1995	26482
1996	26799
1997	26973
1998	27066
1999	27041
2000	26969
2001	26795
2002	26627
2003	26500
2004	26471
2005	26521
2006	26584
2007	26797
2008	27119
2009	27521
2010	28096
2011	28762
2012	29504
2013	30514
2014	31509
2015	32657
2016	33980
2017	35286
2018	36533
2019	37656
2020	38708
2021	39663
2022	40559