Year | Value | 2021 | 23.774833274975 | 2020 | 24.234482597904 | 2019 | 24.598620384893 | 2018 | 25.102987335756 | 2017 | 25.582520832209 | 2016 | 26.06567670064 | 2015 | 27.058078628706 | 2014 | 27.526112160588 | 2013 | 27.873278434089 | 2012 | 28.03156007685 | 2011 | 28.113981304332 | 2010 | 28.107537012617 | 2009 | 27.925863188839 | 2008 | 27.971228198964 | 2007 | 27.989731533993 | 2006 | 27.87098717541 | 2005 | 27.859476135576 | 2004 | 27.994116363412 | 2003 | 28.202106089312 | 2002 | 28.36912402169 | 2001 | 28.701854339157 | 2000 | 28.965076048467 | 1999 | 29.313951416081 | 1998 | 29.726607849488 | 1997 | 30.218697118436 | 1996 | 30.811885444494 | 1995 | 31.684766317446 | 1994 | 32.597402697891 | 1993 | 33.351750591967 | 1992 | 34.112574199508 | 1991 | 34.655143048106 | 1990 | 35.365680251176 | 1989 | 36.189492644574 | 1988 | 37.153461486968 | 1987 | 38.009177843095 | 1986 | 38.852026966912 | 1985 | 39.632135085571 | 1984 | 40.276906026152 | 1983 | 40.942660305168 | 1982 | 41.4013292809 | 1981 | 41.775934981094 | 1980 | 42.217183263059 | 1979 | 42.568146728398 | 1978 | 42.755660363733 | 1977 | 43.022561119865 | 1976 | 43.3925974199 | 1975 | 43.760486006599 | 1974 | 43.917229456631 | 1973 | 44.185395747464 | 1972 | 44.626271259968 | 1971 | 44.952521061902 | 1970 | 45.244285456199 | 1969 | 45.566670611274 | 1968 | 45.905681335899 | 1967 | 46.313852058623 | 1966 | 46.665086057049 | 1965 | 46.941114718154 | 1964 | 47.348272403716 | 1963 | 47.64148425841 | 1962 | 47.942591664946 | 1961 | 47.565064347135 | 1960 | 47.609964701232 |
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