Year | Value | 2021 | 17.773381294964 | 2020 | 17.773381294964 | 2019 | 17.773381294964 | 2018 | 19.845323741007 | 2017 | 22.302158273381 | 2016 | 24.314487632509 | 2015 | 26.720848056537 | 2014 | 23.851590106007 | 2013 | 21.554770318021 | 2012 | 19.257950530035 | 2011 | 16.96113074205 | 2010 | 14.664310954064 | 2009 | 12.332155477032 | 2008 | 13.074204946997 | 2007 | 13.604240282686 | 2006 | 14.204946996466 | 2005 | 14.840989399293 | 2004 | 15.194346289753 | 2003 | 15.901060070671 | 2002 | 16.60777385159 | 2001 | 16.96113074205 | 2000 | 16.96113074205 | 1999 | 17.950530035336 | 1998 | 18.021201413428 | 1997 | 18.021201413428 | 1996 | 18.021201413428 | 1995 | 18.021201413428 | 1994 | 18.021201413428 | 1993 | 18.374558303887 | 1992 | 18.374558303887 | 1991 | 19.081272084806 | 1990 | 19.081272084806 | 1989 | 19.151943462897 | 1988 | 27.208480565371 | 1987 | 27.102473498233 | 1986 | 27.703180212014 | 1985 | 27.56183745583 | 1984 | 27.56183745583 | 1983 | 27.420494699647 | 1982 | 27.208480565371 | 1981 | 27.208480565371 | 1980 | 26.148409893993 | 1979 | 25.971731448763 | 1978 | 25.088339222615 | 1977 | 25.088339222615 | 1976 | 24.381625441696 | 1975 | 22.968197879859 | 1974 | 22.614840989399 | 1973 | 22.614840989399 | 1972 | 22.614840989399 | 1971 | 22.614840989399 | 1970 | 22.43816254417 | 1969 | 22.26148409894 | 1968 | 22.26148409894 | 1967 | 21.908127208481 | 1966 | 21.908127208481 | 1965 | 21.908127208481 | 1964 | 20.141342756184 | 1963 | 20.141342756184 | 1962 | 20.141342756184 | 1961 | 19.787985865724 |
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