Year | Value | 2021 | 2.5140770050221 | 2020 | 2.5140770050221 | 2019 | 2.5140770050221 | 2018 | 2.5140770050221 | 2017 | 2.5140770050221 | 2016 | 2.5140770050221 | 2015 | 2.5119768680566 | 2014 | 2.4471161162684 | 2013 | 2.4431593364785 | 2012 | 2.6431288997109 | 2011 | 2.6346066047786 | 2010 | 2.6002130573733 | 2009 | 2.5719068634911 | 2008 | 2.6492162532339 | 2007 | 2.5177294171359 | 2006 | 2.7094810531122 | 2005 | 2.8896971541622 | 2004 | 2.8814487901385 | 2003 | 2.8800486988282 | 2002 | 2.9447572667783 | 2001 | 2.66930451986 | 2000 | 2.6440420027393 | 1999 | 2.6696088875361 | 1998 | 2.6623040633085 | 1997 | 2.7049155379699 | 1996 | 2.7152640389591 | 1995 | 2.7423527621367 | 1994 | 2.8242276670218 | 1993 | 2.7861817075027 | 1992 | 2.8199665195556 | 1991 | 2.8504032871709 | 1990 | 2.8324455942779 | 1989 | 2.7627453964389 | 1988 | 2.7752244711612 | 1987 | 2.7435702328413 | 1986 | 2.7237863338913 | 1985 | 2.8846446507381 | 1984 | 2.8949018414244 | 1983 | 3.0145792116877 | 1982 | 3.0278192056004 | 1981 | 3.1465225993 | 1980 | 3.2202100136965 | 1979 | 3.293593060417 | 1978 | 3.2719525186425 | 1977 | 3.2498554253538 | 1976 | 3.1612235580581 | 1975 | 3.2115050981586 | 1974 | 3.057281996652 | 1973 | 3.0920407852686 | 1972 | 3.0650738091615 | 1971 | 2.9456094962715 | 1970 | 2.8945670369807 | 1969 | 2.6447724851621 | 1968 | 2.6336935017501 | 1967 | 2.4004869882818 | 1966 | 2.3653325216862 | 1965 | 2.35379698676 | 1964 | 2.4684827271344 | 1963 | 2.4375894080049 | 1962 | 2.3678283366306 | 1961 | 2.2971845989956 |
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