Year	Number
1960	-4
1961	-4
1962	-7
1963	-7
1964	-7
1965	-7
1966	-7
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	-6
1992	-6
1993	-6
1994	-6
1995	-6
1996	-6
1997	-6
1998	-6
1999	-6
2000	-6
2001	-6
2002	-6
2003	-6
2004	-6
2005	-5
2006	-3
2007	4
2008	-5
2009	-2
2010	-2
2011	-2