Year | Value | 2021 | 15.993279205041 | 2020 | 16.056366941347 | 2019 | 16.063136209404 | 2018 | 16.082767813863 | 2017 | 16.104459524964 | 2016 | 16.292898691226 | 2015 | 16.312409112942 | 2014 | 16.380271449346 | 2013 | 16.406931652933 | 2012 | 16.421473582162 | 2011 | 16.476005816772 | 2010 | 16.526902569074 | 2009 | 16.560833737276 | 2008 | 16.589917595734 | 2007 | 16.674745516238 | 2006 | 16.689287445468 | 2005 | 16.73170140572 | 2004 | 16.714735821619 | 2003 | 16.7235821619 | 2002 | 16.783809985458 | 2001 | 16.808046534173 | 2000 | 16.953465826466 | 1999 | 16.989820649539 | 1998 | 17.014057198255 | 1997 | 17.03829374697 | 1996 | 17.086766844401 | 1995 | 17.135239941832 | 1994 | 17.244304411052 | 1993 | 17.195831313621 | 1992 | 17.401841977702 | 1991 | 17.510906446922 | 1990 | 17.280659234125 | 1989 | 17.68056228793 | 1988 | 17.668444013573 | 1987 | 17.438196800776 | 1986 | 17.438196800776 | 1985 | 17.547261269995 | 1984 | 17.510906446922 | 1983 | 17.438196800776 | 1982 | 18.601551139118 | 1981 | 18.771206980126 | 1980 | 18.613669413475 | 1979 | 18.456131846825 | 1978 | 18.746970431411 | 1977 | 18.528841492971 | 1976 | 18.419777023752 | 1975 | 18.310712554532 | 1974 | 18.347067377605 | 1973 | 18.347067377605 | 1972 | 19.243819680078 | 1971 | 19.23170140572 | 1970 | 19.219583131362 | 1969 | 19.207464857004 | 1968 | 19.401357246728 | 1967 | 19.38923897237 | 1966 | 19.583131362094 | 1965 | 20.116335433834 | 1964 | 20.079980610761 | 1963 | 20.067862336403 | 1962 | 20.370819195347 | 1961 | 20.467765390208 |
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