Year	Number
1970	18600
1971	19500
1972	21500
1973	13700
1974	16100
1975	12600
1976	23800
1977	19800
1978	20100
1979	21100
1980	20700
1981	19500
1982	20000
1983	29200
1984	26500
1985	27700
1986	21600
1987	24000
1988	23300
1989	25200
1990	21300
1991	20900
1992	20000
1993	20000
1994	18700
1995	17000
1996	18300
1997	12300
1998	12500
1999	20600
2000	16577
2001	24440
2002	23343
2003	23976
2004	23338
2005	21787
2006	21133
2007	22401
2008	22894
2009	16840
2010	0
2011	0
2012	0
2013	492
2014	953
2015	997
2016	1128
2017	1181
2018	1215.272