Year	Number
1980	226976
1981	179687
1982	174308
1983	203770
1984	197893
1985	192280
1986	184275
1987	186813
1988	204262
1989	207650
1990	198907
1991	188081
1992	194643
1993	187369
1994	199891
1995	240489
1996	263425
1997	278339
1998	283692
1999	303074
2000	319697
2001	361604
2002	360417
2003	353953
2004	370887
2005	398533
2006	429401
2007	445262
2008	449643
2009	427157
2010	447311
2011	460503
2012	484332
2013	502380
2014	516949
2015	528063
2016	534859
2017	539128