Year	Number
1919	10
1920	10
1921	10
1922	10
1923	10
1924	10
1925	10
1926	10
1927	10
1928	10
1929	10
1930	10
1931	10
1932	10
1933	6
1934	2
1935	-2
1936	-6
1937	-6
1938	-6
1939	-6
1940	-6
1941	-9
1942	-9
1943	-9
1944	-9
1945	-9
1946	-9
1947	-9
1948	-9
1949	-9
1950	-9
1951	-9
1952	-9
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	-7
1981	-7
1982	-7
1983	-7
1984	-7
1985	-7
1986	-7
1987	-7
1988	-6
1989	-4
1990	0
1991	6
1992	6
1993	6
1994	6
1995	6
1996	6
1997	6
1998	6
1999	7
2000	9
2001	9
2002	9
2003	9
2004	9
2005	9
2006	9
2007	9
2008	9
2009	9
2010	9
2011	9