Year	Number
1970	1400
1971	1300
1972	1000
1973	1100
1974	1000
1975	1100
1976	1200
1977	1100
1978	1100
1979	1200
1980	1100
1981	1600
1982	2000
1983	2000
1984	2000
1985	2100
1986	2700
1987	2600
1988	2600
1989	1100
1990	500
1991	1200
1992	1100
1993	1300
1994	1300
1995	1300
1996	1500
1997	1500
1998	1500
1999	1500
2000	1518
2001	716
2010	1255.45454545455
2011	1381
2012	1381
2013	1728
2014	648
2015	1209
2016	10