Year	Number
1971	23484
1972	25430
1973	27256
1974	28422
1975	29090
1976	29859
1977	30899
1978	31091
1979	31441
1980	30610
1981	29605
1982	31199
1983	31795
1984	32107
1985	33032
1986	32817
1987	32798
1988	32809
1989	33120
1990	33148
1991	33006
1992	32622
1993	32545
1994	31928
1995	30486
1996	31194
1997	31615
1998	31548
1999	25581
2000	25347
2001	25481
2002	24954
2003	24573
2004	23821
2005	23573
2006	24046
2007	22028
2008	20938
2009	20187
2010	19483
2011	18894
2012	18172
2013	17748
2014	17286
2015	16822
2016	16445
2017	16054
2018	15874
2019	15693
2020	15478
2021	15424
2022	15388