Year	Ratio
1935	260
1940	240
1947	168
1950	176
1951	173
1952	170
1953	181
1954	184
1955	179
1956	170
1957	171
1958	155
1959	146
1960	131
1961	120
1962	112
1963	103
1964	99
1965	88
1966	93
1967	71
1968	68
1969	58
1970	51.7
1971	46
1972	41.3
1973	38
1974	34
1975	30
1976	26
1977	23.7
1978	22
1979	22
1980	19.6
1990	14
1995	10
2000	10
2005	7
2010	6
2013	6