Year | Value | 2021 | 19.88753887876 | 2020 | 19.88753887876 | 2019 | 19.885705530872 | 2018 | 20.026505285736 | 2017 | 19.997855227882 | 2016 | 19.547167499004 | 2015 | 19.52134485821 | 2014 | 19.342193911925 | 2013 | 19.273289642923 | 2012 | 19.213044476766 | 2011 | 19.222703546664 | 2010 | 19.17460123075 | 2009 | 19.04331853666 | 2008 | 18.791997673386 | 2007 | 18.337617823479 | 2006 | 17.746797863712 | 2005 | 17.23858209869 | 2004 | 16.95999510269 | 2003 | 16.803868164152 | 2002 | 16.716650855342 | 2001 | 16.738072650488 | 2000 | 16.543746365945 | 1999 | 16.233130336322 | 1998 | 16.086238026747 | 1997 | 16.095418796095 | 1996 | 16.072466872724 | 1995 | 15.989839948588 | 1994 | 15.94546623007 | 1993 | 15.983719435689 | 1992 | 15.910273280901 | 1991 | 15.937815588946 | 1990 | 15.956177127643 | 1989 | 15.905682896227 | 1988 | 15.872020075282 | 1987 | 15.946996358295 | 1986 | 15.966888025216 | 1985 | 15.957707255868 | 1984 | 15.946996358295 | 1983 | 15.971478409891 | 1982 | 15.976068794565 | 1981 | 15.94546623007 | 1980 | 15.890381613979 | 1979 | 15.878140588181 | 1978 | 15.862839305934 | 1977 | 15.846007895462 | 1976 | 15.85518866481 | 1975 | 15.832236741439 | 1974 | 15.810814946292 | 1973 | 15.79398353582 | 1972 | 16.533035468372 | 1971 | 16.533035468372 | 1970 | 16.526914955473 | 1969 | 16.474890595832 | 1968 | 16.476420724057 | 1967 | 16.474890595832 | 1966 | 16.433577133764 | 1965 | 16.193347002479 | 1964 | 16.249961746794 | 1963 | 16.077057257398 | 1962 | 16.020442513083 | 1961 | 15.959237384093 |
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