Year | Value | 2021 | 28.639094463601 | 2020 | 28.56461856346 | 2019 | 28.490129502497 | 2018 | 28.415628477149 | 2017 | 28.341066313797 | 2016 | 28.254970603507 | 2015 | 28.168731320605 | 2014 | 28.082492037702 | 2013 | 27.996252754799 | 2012 | 27.910013471897 | 2011 | 27.823774188994 | 2010 | 27.737534906092 | 2009 | 27.651295623189 | 2008 | 27.565056340286 | 2007 | 27.478817057384 | 2006 | 27.392577774481 | 2005 | 27.379536595463 | 2004 | 27.367129528819 | 2003 | 27.354722462175 | 2002 | 27.342315395531 | 2001 | 27.329908328887 | 2000 | 27.317501262243 | 1999 | 27.305094195598 | 1998 | 27.292687128955 | 1997 | 27.28028006231 | 1996 | 27.267872995667 | 1995 | 27.255465929022 | 1994 | 27.424857683647 | 1993 | 27.594728013649 | 1992 | 27.764598343651 | 1991 | 27.934468673652 | 1990 | 28.104339003654 | 1989 | 28.274209333656 | 1988 | 28.444079663657 | 1987 | 28.613949993659 | 1986 | 28.78382032366 | 1985 | 28.953655598016 | 1984 | 28.726989497663 | 1983 | 28.500049053976 | 1982 | 28.273108610289 | 1981 | 28.046168166602 | 1980 | 27.819252608834 | 1979 | 27.224119241841 | 1978 | 26.63535188451 | 1977 | 26.04658452718 | 1976 | 25.457817169849 | 1975 | 24.869049812518 | 1974 | 24.449458850893 | 1973 | 24.029987533111 | 1972 | 23.61051621533 | 1971 | 23.191044897549 | 1970 | 22.771573579768 | 1969 | 22.327335986236 | 1968 | 21.88381625577 | 1967 | 21.440296525303 | 1966 | 20.996776794837 | 1965 | 20.553257064371 | 1964 | 20.109737333904 | 1963 | 19.666217603438 | 1962 | 19.222697872972 | 1961 | 18.779178142505 |
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