Year	Number
1970	4000
1971	4100
1972	3900
1973	4000
1974	3800
1975	4000
1976	4200
1977	4200
1978	4300
1979	4400
1980	4500
1981	2400
1982	2600
1983	2600
1984	2000
1985	2100
1986	2100
1987	1600
1988	1700
1989	1700
1990	1200
1991	1800
1992	1700
1993	1900
1994	1900
1995	2000
1996	2100
1997	1800
1998	1800
1999	1500
2000	1518
2001	716
2010	699.531448355453
2011	984
2012	664
2013	72
2014	72