| Year | Value | | 2021 | 44.363367353855 | | 2020 | 44.363367353855 | | 2019 | 44.363367353855 | | 2018 | 44.363367353855 | | 2017 | 44.363367353855 | | 2016 | 44.30370530707 | | 2015 | 44.244027277637 | | 2014 | 44.184360180248 | | 2013 | 44.124682150814 | | 2012 | 44.064999070776 | | 2011 | 44.278758382145 | | 2010 | 44.492512642909 | | 2009 | 44.706266903673 | | 2008 | 44.920021164438 | | 2007 | 45.062345010653 | | 2006 | 45.066841884671 | | 2005 | 45.071295099717 | | 2004 | 45.075802888477 | | 2003 | 45.080321591981 | | 2002 | 45.084873039712 | | 2001 | 45.290070203625 | | 2000 | 45.230584855576 | | 1999 | 45.189300968669 | | 1998 | 45.265838042747 | | 1997 | 45.298265305231 | | 1996 | 45.453413924725 | | 1995 | 45.871911221361 | | 1994 | 45.981093923327 | | 1993 | 46.178605431184 | | 1992 | 46.449487714762 | | 1991 | 46.615336239049 | | 1990 | 46.615336239049 | | 1989 | 46.615336239049 | | 1988 | 46.615336239049 | | 1987 | 46.615336239049 | | 1986 | 47.1013084455 | | 1985 | 47.1013084455 | | 1984 | 47.1013084455 | | 1983 | 47.1013084455 | | 1982 | 47.1013084455 | | 1981 | 46.747993221938 | | 1980 | 46.747993221938 | | 1979 | 46.747993221938 | | 1978 | 46.747993221938 | | 1977 | 46.984701319801 | | 1976 | 46.96581271236 | | 1975 | 46.96581271236 | | 1974 | 46.96581271236 | | 1973 | 47.079581087809 | | 1972 | 47.199682059972 | | 1971 | 47.308864761938 | | 1970 | 47.428965734101 | | 1969 | 47.543280023059 | | 1968 | 47.581275603344 | | 1967 | 47.527994444784 | | 1966 | 47.554525841362 | | 1965 | 47.589791854097 | | 1964 | 47.932516355569 | | 1963 | 48.197939504048 | | 1962 | 48.476137028658 | | 1961 | 48.860241774175 |
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