1928	0.2065
1929	0.2069
1930	0.2067
1931	0.2080
1932	0.2098
1933	0.2410
1934	0.2007
1935	0.2063
1936	0.2034
1937	0.2042
1938	0.2065
1939	0.2272
1940	0.2513
1941	0.2513
1942	0.2513
1943	0.2513
1944	0.2513
1945	0.2506
1946	0.2497
1947	0.2495
1948	0.2495
1949	0.2728
1950	0.3592
1951	0.3593
1952	0.3595
1953	0.3569
1954	0.3574
1955	0.3596
1956	0.3590
1957	0.3593
1958	0.3572
1959	0.3574
1960	0.3575
1961	0.7164
1962	0.7149
1963	0.7169
1964	0.7190
1965	0.7180
1966	0.7188
1967	0.7190
1968	0.7189
1969	0.7199
1970	0.7182
1971	0.7128
1972	0.7726
1973	0.6950
1974	0.6804
1975	0.7328
1976	0.8707
1977	0.8696
1978	0.8695
1979	0.8423
1980	0.7780
1981	0.8713
1982	1.0835
1983	1.1130
1984	1.4382
1985	2.2343
1986	2.2919
1987	2.0385
1988	2.2770
1989	2.6214
1990	2.5885
1991	2.7633
1992	2.8524
1993	3.2729
1994	3.5526
1995	3.6284
1996	4.3011
1997	4.6072
1998	5.5417
1999	6.1191
2000	6.9468
2001	8.6093
2002	10.517
2003	7.5550
2004	6.4402
2005	6.3606
2006	6.7668
2007	7.0477
2008	8.2480
2009	8.4117
2010	7.3161
2011	7.2510