Year	Number
1960	-1
1961	-1
1962	-1
1963	-1
1964	-1
1965	-1
1966	-1
1967	-1
1968	-1
1969	-1
1970	-1
1971	-1
1972	-3
1973	-3
1974	-3
1975	-6
1976	-6
1977	-6
1978	-6
1979	-6
1980	-6
1981	-6
1982	-6
1983	-6
1984	-6
1985	-6
1986	-6
1987	-6
1988	-6
1989	-6
1990	-6
1991	2
1992	9
1993	9
1994	9
1995	9
1996	9
1997	8
1998	7
1999	7
2000	7
2001	7
2002	7
2003	7
2004	7
2005	7
2006	7
2007	7
2008	7
2009	0
2010	0
2011	0