| Year | Value | | 2022 | 47.610598974151 | | 2021 | 47.468043505386 | | 2020 | 47.505597522341 | | 2019 | 47.533728188954 | | 2018 | 47.551639375308 | | 2017 | 47.560608280569 | | 2016 | 47.559798494507 | | 2015 | 47.555309288983 | | 2014 | 47.544644996789 | | 2013 | 47.534164781225 | | 2012 | 47.527522738283 | | 2011 | 47.517666974676 | | 2010 | 47.501295475541 | | 2009 | 47.479125172157 | | 2008 | 47.451803604113 | | 2007 | 47.422013220551 | | 2006 | 47.395243114701 | | 2005 | 47.370033653373 | | 2004 | 47.366626348686 | | 2003 | 47.373632810306 | | 2002 | 47.368938784977 | | 2001 | 47.363421648989 | | 2000 | 47.354543835893 | | 1999 | 47.335022019369 | | 1998 | 47.301778279439 | | 1997 | 47.257139566784 | | 1996 | 47.204355564484 | | 1995 | 47.156244543266 | | 1994 | 47.106295651072 | | 1993 | 47.050585832709 | | 1992 | 47.008344119627 | | 1991 | 46.962019200045 | | 1990 | 46.908452057598 | | 1989 | 46.866057479252 | | 1988 | 46.828861413112 | | 1987 | 46.787625701182 | | 1986 | 46.743603859108 | | 1985 | 46.704660525799 | | 1984 | 46.669892055122 | | 1983 | 46.641101018604 | | 1982 | 46.61199845957 | | 1981 | 46.58131075642 | | 1980 | 46.550335832172 | | 1979 | 46.514281303148 | | 1978 | 46.475185978972 | | 1977 | 46.433333683841 | | 1976 | 46.389289550717 | | 1975 | 46.345397801403 | | 1974 | 46.299067655472 | | 1973 | 46.250973892503 | | 1972 | 46.209887850053 | | 1971 | 46.175510224754 | | 1970 | 46.145766529961 | | 1969 | 46.119508900979 | | 1968 | 46.095477920541 | | 1967 | 46.071559784256 | | 1966 | 46.047588046215 | | 1965 | 46.026370255833 | | 1964 | 46.008155083419 | | 1963 | 45.99021726766 | | 1962 | 45.976056471195 | | 1961 | 45.966168416159 | | 1960 | 45.960462354469 |
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