Year	Number
1970	16000
1971	38100
1972	39100
1973	39700
1974	33100
1975	29400
1976	27500
1977	30300
1978	34000
1979	39800
1980	37100
1981	34900
1982	38900
1983	41700
1984	47900
1985	49100
1986	53100
1987	59100
1988	69200
1989	143600
1990	120100
1991	120100
1992	141000
1993	163500
1994	170300
1995	188900
1996	207300
1997	229300
1998	207900
1999	204000
2000	226910
2001	228442
2002	238649
2003	240942
2004	232077
2005	221424
2006	223735
2007	243113
2008	250260
2009	256160
2010	280427
2011	282239
2012	285000
2013	360356
2014	368132
2015	448037
2016	473606
2017	499093.92
2018	527807
2019	549454
2020	254341
2021	287163