Year	Number
1970	27941
1971	29692
1972	30652
1973	30772
1974	30747
1975	30109
1976	30824
1977	32188
1978	33053
1979	29934
1980	30513
1981	31677
1982	31682
1983	32771
1984	34373
1985	34815
1986	36983
1987	36861
1988	38146
1989	39862
1991	38933
1992	39782
1993	41134
1994	42270
1995	42672
1996	43291
1997	43540
1998	45369
1999	45827
2000	45428
2001	44487
2002	44882
2003	46242
2004	46382
2005	46012
2006	46086
2007	45972
2008	45125
2009	44681
2010	44215
2011	43487
2012	42753
2013	42090
2014	41078
2015	40397
2016	40471
2017	39610
2018	39404
2019	39236
2020	39649