Year	Ratio
1847	597.4
1848	611.8
1849	577.5
1850	548
1851	534.2
1852	520.3
1853	499.7
1854	474.3
1855	409
1856	445.4
1857	422.2
1858	472
1859	504.2
1860	473.2
1861	436.3
1862	428.4
1863	497
1864	544.7
1865	517.6
1866	474.7
1867	441.5
1868	443
1869	433.8
1870	490.8
1871	501.3
1872	467.1
1873	494
1874	689.4
1875	587.6
1876	467.9
1877	394.1
1878	377.3
1879	389.7
1880	408.6
1881	489.3
1882	512.2
1883	521.8
1884	487.8
1885	512.3
1886	431.5
1887	472.1
1888	480.4
1889	417.1
1890	498.4
1891	529.3
1892	574.9
1893	627.6
1894	532.4
1895	460.2
1896	491.9
1897	459.4
1898	437.3
1899	464.7
1900	474.4
1901	472.7
1902	455.5
1903	422
1904	397.2
1905	435.8
1906	419.3
1907	401.7
1908	376.6
1909	391
1910	382
1911	409.7
1912	416.7
1913	419.1
1914	439.9
1915	441.7
1916	431.3
1917	414.4
1918	420.3
1919	461.6
1920	455.7
1921	422.3
1922	415.6
1923	414.6
1924	414.5
1925	434.6
1926	441.3
1927	440.9
1928	474.7
1929	465
1930	472.4
1931	420
1932	433.6
1933	452.8
1934	464.2
1935	457.8
1936	421.3
1937	367.4
1938	356.1
1939	340.4
1940	298.6
1941	316.2
1942	276.2
1943	253.7
1944	209.3
1945	196
1946	155.5
1947	129.4
1948	111
1949	103
1950	91.4
1951	76
1952	67
1953	71
1954	65
1955	60.6
1956	53.4
1957	46
1958	44.3
1959	38.7
1960	39.5
1961	33.8
1962	35.6
1963	28.5
1964	25.9
1965	26.9
1966	26.1
1967	20.9
1968	23.4
1969	18.9
1970	18
1971	16.8
1972	15.4
1973	14.4
1974	13.3
1975	13.2
1976	13
1977	12.5
1978	11.7
1979	11.7
1980	10.3
1990	10
1995	11
2000	11
2005	12
2010	11
2013	8