Year	Number
1971	16200
1972	18737
1973	18495
1976	11360
1977	9401
1978	9423
1979	10676
1980	12448
1981	12704
1982	18014
1983	15638
1985	16820
1986	15338
1987	13606
1990	14836
1991	14077
1992	13804
1993	16546
1994	18837
1995	19313
1999	20573
2000	20047
2001	20880
2002	22455
2004	23506
2005	25287
2006	26269
2007	27781
2008	29487
2009	37325
2010	35162
2011	34176
2012	32331
2013	48249
2014	52560
2015	52416
2017	112327