Year	Number
1960	-6
1961	-6
1962	-6
1963	-6
1964	-6
1965	-6
1966	-6
1967	-7
1968	-7
1969	-7
1970	-7
1971	-7
1972	-7
1973	-7
1974	-7
1975	-7
1976	-7
1977	-7
1978	-7
1979	-7
1980	-7
1981	-7
1982	-7
1983	-7
1984	-7
1985	-7
1986	-7
1987	-7
1988	-7
1989	-7
1990	-7
1991	-5
1992	-3
1993	-2
1994	-2
1995	-2
1996	-2
1997	-2
1998	-2
1999	-2
2000	-2
2001	-2
2002	-2
2003	-2
2004	-2
2005	-4
2006	-4
2007	-4
2008	-4
2009	-4
2010	-2
2011	-2