Year | Value | 2021 | 32.067958944834 | 2020 | 32.067958944834 | 2019 | 32.067958944834 | 2018 | 32.067958944834 | 2017 | 32.067958944834 | 2016 | 31.933440051655 | 2015 | 31.933440051655 | 2014 | 31.932094862723 | 2013 | 31.930749673792 | 2012 | 32.063923378038 | 2011 | 31.794885591681 | 2010 | 31.525847805324 | 2009 | 31.727626145092 | 2008 | 31.056376868131 | 2007 | 30.917822408157 | 2006 | 31.003914499791 | 2005 | 30.619190465301 | 2004 | 30.800790971092 | 2003 | 30.816933238273 | 2002 | 30.42279288126 | 2001 | 30.340736356421 | 2000 | 30.3017258774 | 1999 | 30.070353381132 | 1998 | 29.828219373411 | 1997 | 29.603572821803 | 1996 | 29.370855136604 | 1995 | 29.127375939951 | 1994 | 28.885241932229 | 1993 | 28.520695731715 | 1992 | 28.336404848061 | 1991 | 28.014904693364 | 1990 | 27.994726859387 | 1989 | 27.926122223866 | 1988 | 27.733760206621 | 1987 | 27.60462206917 | 1986 | 27.474138742786 | 1985 | 27.346345794267 | 1984 | 27.202410578566 | 1983 | 27.086724330432 | 1982 | 26.956241004049 | 1981 | 26.840554755916 | 1980 | 26.696619540214 | 1979 | 26.607837070717 | 1978 | 27.112282920136 | 1977 | 27.272360403019 | 1976 | 27.260253702633 | 1975 | 27.222588412542 | 1974 | 27.17550679993 | 1973 | 27.097485841886 | 1972 | 27.028881206365 | 1971 | 26.975073649094 | 1970 | 26.734284830304 | 1969 | 26.640121605079 | 1968 | 26.547303568786 | 1967 | 26.447759587834 | 1966 | 26.375119385518 | 1965 | 26.24867162593 | 1964 | 26.176031423613 | 1963 | 26.102046032365 | 1962 | 26.042857719367 | 1961 | 25.971562705982 |
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