Year	Number
1948	-7
1949	-7
1950	-7
1951	-7
1952	-7
1953	-7
1954	-7
1955	-7
1956	-8
1957	-8
1958	-8
1959	-8
1960	-8
1961	-8
1962	-8
1963	-8
1964	-8
1965	-8
1966	-9
1967	-9
1968	-9
1969	-9
1970	-9
1971	-9
1972	-9
1973	-9
1974	-9
1975	-9
1976	-9
1977	-9
1978	-9
1979	-9
1980	-9
1981	-9
1982	-9
1983	-9
1984	-9
1985	-9
1986	-9
1987	-9
1988	-9
1989	-9
1990	-9
1991	-9
1992	-9
1993	-9
1994	-10
1995	-10
1996	-10
1997	-10
1998	-10
1999	-10
2000	-10
2001	-10
2002	-10
2003	-10
2004	-10
2005	-10
2006	-10
2007	-10
2008	-10
2009	-10
2010	-10
2011	-10