Year | Value | 2021 | 12.812651927622 | 2020 | 12.974346309134 | 2019 | 13.253184321698 | 2018 | 13.708221812951 | 2017 | 14.054863460689 | 2016 | 14.786860313587 | 2015 | 15.043086169731 | 2014 | 15.078195261091 | 2013 | 14.878958103515 | 2012 | 14.867959781032 | 2011 | 14.534025423174 | 2010 | 14.614801662978 | 2009 | 14.640894484244 | 2008 | 14.499371536762 | 2007 | 13.907358732816 | 2006 | 13.341588812684 | 2005 | 13.038777938328 | 2004 | 13.046389578766 | 2003 | 12.710657228661 | 2002 | 12.613478426185 | 2001 | 12.58542820847 | 2000 | 12.589239453916 | 1999 | 12.625095912669 | 1998 | 13.103387145184 | 1997 | 13.341667572454 | 1996 | 13.76394878699 | 1995 | 14.215812435013 | 1994 | 14.629206110345 | 1993 | 14.962050850657 | 1992 | 15.820722545746 | 1991 | 16.817418603517 | 1990 | 17.514410584173 | 1989 | 18.3676270136 | 1988 | 19.38811375095 | 1987 | 20.108062377445 | 1986 | 20.419946300692 | 1985 | 20.240513706783 | 1984 | 20.484759931792 | 1983 | 20.70281437283 | 1982 | 20.234710904568 | 1981 | 20.091433460025 | 1980 | 20.218908163187 | 1979 | 20.296537077448 | 1978 | 20.545158085461 | 1977 | 20.572371068356 | 1976 | 20.680758533074 | 1975 | 20.667609626306 | 1974 | 20.737507310118 | 1973 | 20.466961137148 | 1972 | 20.503886774716 | 1971 | 20.452644002932 | 1970 | 20.191565508304 | 1969 | 20.185224731341 | 1968 | 20.410814181893 | 1967 | 20.69586451598 | 1966 | 20.584928605808 | 1965 | 21.272164238476 | 1964 | 22.193616304741 | 1963 | 23.46900202114 | 1962 | 24.60375197822 | 1961 | 25.661257614699 | 1960 | 26.591508471361 |
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