Year	Ratio
1875	660
1885	710
1895	660
1901	618
1902	623
1903	563
1904	562
1905	557
1906	586
1907	496
1908	520
1909	546
1910	531
1911	505
1912	543
1913	536
1914	521
1915	530
1916	574
1917	485
1918	483
1919	471
1920	487
1921	495
1922	566
1923	482
1924	478
1925	469
1926	489
1927	451
1928	493
1929	410
1930	477
1931	431
1932	455
1933	444
1934	468
1935	467
1936	470
1937	361
1938	411
1939	339
1940	367
1941	321
1942	247
1943	225
1944	238
1945	237
1946	201
1947	188
1948	158
1949	181
1950	156
1951	163.8
1952	142.3
1953	132.7
1954	110.3
1955	113.6
1956	85.6
1957	132.3
1958	102.5
1959	64.8
1960	57.6
1961	45.1
1962	43.7
1963	34.8
1964	46.8
1965	28.3
1966	28.9
1967	22.8
1968	36.1
1969	31.8
1970	29.3
1971	32.5
1972	26.1
1973	24.9
1974	13.6
1975	15.2
1976	11.8
1977	15
1978	12.8
1979	12.8
1980	10.6
1990	6
1995	4
2000	6
2005	2
2010	10
2013	9