Year	Number
1918	8
1919	8
1920	8
1921	8
1922	8
1923	8
1924	8
1925	8
1926	-3
1927	-3
1928	-3
1929	-3
1930	-3
1931	-3
1932	-3
1933	-3
1934	-3
1935	-6
1936	-6
1937	-6
1938	-6
1939	0
1940	0
1941	0
1942	0
1943	0
1944	0
1945	-2
1946	-5
1947	-7
1948	-7
1949	-7
1950	-7
1951	-7
1952	-7
1953	-7
1954	-7
1955	-7
1956	-7
1957	-7
1958	-7
1959	-7
1960	-7
1961	-7
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	-6
1981	-8
1982	-8
1983	-7
1984	-7
1985	-7
1986	-7
1987	-6
1988	-6
1989	5
1990	5
1991	8
1992	8
1993	8
1994	8
1995	9
1996	9
1997	9
1998	9
1999	9
2000	9
2001	9
2002	10
2003	10
2004	10
2005	10
2006	10
2007	10
2008	10
2009	10
2010	10
2011	10