Year	Ratio
1875	643
1885	592
1895	560
1903	609
1906	538
1907	556.4
1908	543.3
1909	505.8
1910	505.1
1911	503.3
1912	483.9
1913	488.5
1914	459.5
1915	425.6
1916	527.3
1917	563.2
1918	470.8
1919	466.1
1920	500
1921	472.1
1922	451.6
1923	511
1924	547
1925	564.1
1926	530.2
1927	592.4
1928	598.2
1929	508.2
1930	529.6
1931	548.5
1932	555.3
1933	513.2
1934	576.4
1935	421.3
1936	599.6
1937	462.5
1938	466.7
1939	409.3
1940	407.6
1941	364.2
1942	359.2
1943	332.9
1944	285
1945	215.5
1946	185.4
1947	187
1948	140.5
1949	121.4
1950	109.1
1951	105
1952	94.2
1953	62.3
1954	68.7
1955	64
1956	56.1
1957	62.6
1958	49.9
1959	45.8
1960	52.5
1961	45
1962	35.9
1963	27.2
1964	32.7
1965	33.2
1966	29.5
1967	23.1
1968	28.2
1969	17.6
1970	20.6
1971	18.8
1972	14.1
1973	11.7
1974	9.4
1975	10.1
1976	8.9
1977	9.3
1978	7.6
1979	7.6
1980	8.6
1990	7
1995	8
2000	9
2005	6
2010	5
2013	6