Year	Number
1910	4
1911	4
1912	4
1913	4
1914	4
1915	4
1916	4
1917	4
1918	4
1919	4
1920	4
1921	4
1922	4
1923	4
1924	4
1925	4
1926	4
1927	4
1928	4
1929	4
1930	4
1931	4
1932	4
1933	4
1934	4
1935	4
1936	4
1937	4
1938	4
1939	4
1940	4
1941	4
1942	4
1943	4
1944	4
1945	4
1946	4
1947	4
1948	4
1949	4
1950	4
1951	4
1952	4
1953	4
1954	4
1955	4
1956	4
1957	4
1958	4
1959	4
1960	4
1961	4
1962	4
1963	4
1964	4
1965	4
1966	4
1967	4
1968	4
1969	4
1970	4
1971	4
1972	4
1973	4
1974	4
1975	4
1976	4
1977	4
1978	4
1979	4
1980	4
1981	4
1982	4
1983	4
1984	4
1985	4
1986	4
1987	4
1988	4
1989	4
1990	5
1991	5
1992	6
1993	8
1994	9
1995	9
1996	9
1997	9
1998	9
1999	9
2000	9
2001	9
2002	9
2003	9
2004	9
2005	9
2006	9
2007	9
2008	9
2009	9
2010	9
2011	9