1919	2.4531278310
1920	2.4688657820
1921	2.9997005330
1922	3.1020942920
1923	2.9584364890
1924	2.9132112500
1925	2.8699435440
1926	2.9129403120
1927	2.8819978260
1928	2.8791984570
1929	2.8154453050
1930	2.8355845740
1931	2.9240762850
1932	2.9469421090
1933	2.9033589530
1934	2.7436773790
1935	2.6421656040
1936	2.5794171490
1937	2.4389215370
1938	2.4931034170
1939	2.5105384790
1940	2.4079456090
1941	2.3855231450
1942	2.3045478020
1943	2.2778924800
1944	2.2528616580
1945	2.1943715080
1946	2.1409155810
1947	2.0596389140
1948	2.0605443020
1949	2.0800766640
1950	2.0726951190
1951	2.0810867300
1952	2.1751620620
1953	2.3538783870
1954	2.4449246120
1955	2.4719144910
1956	2.4771589630
1957	2.4941528040
1958	2.5320511100
1959	2.6106280880
1960	2.6914038100
1961	2.7712650950
1962	2.7942408010
1963	2.8228894610
1964	2.7888236950
1965	2.7818623590
1966	2.7556627150
1967	2.7725887220
1968	2.7725887220
1969	2.7524339200
1970	2.7401385160
1971	2.7703933320
1972	2.7483682900
1973	2.7748134170
1974	2.9305689480
1975	3.2476182940
1976	3.4561270440
1977	3.7057294830
1978	3.7722610630
1979	3.9137193590
1980	4.0797720140
1981	4.2117640280
1982	4.4086210550
1983	4.4472098940
1984	4.4504503880
1985	4.3972494860
1986	4.1691458750
1987	3.9936812890
1988	3.9664666950
1989	3.9182851760
1990	3.8939418450
1991	3.8504232490
1992	3.9036387120
1993	4.0483032710
1994	3.9540924530
1995	3.7514509380
1996	4.0641502643
1997	4.1317736745
1998	3.9885491527
1999	4.0907026450
2000	4.5539286706
2001	4.6260699963
2002	4.3449516393
2003	4.7962740192
2004	4.8481659644
2005	5.0722920397
2006	4.8943993403