Year	Number
1923	-7
1924	-7
1925	-7
1926	-7
1927	-8
1928	-8
1929	-8
1930	-8
1931	-8
1932	-8
1933	-9
1934	-9
1935	-9
1936	-9
1937	-9
1938	-9
1939	-9
1940	-9
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	4
1992	4
1993	4
1994	4
1995	5
1996	5
1997	5
1998	5
1999	5
2000	5
2001	5
2002	5
2003	5
2004	7
2005	7
2006	7
2007	6
2008	6
2009	6
2010	6
2011	6