| Year | Value | | 2022 | 67.966742393981 | | 2021 | 67.227984938712 | | 2020 | 66.467488528042 | | 2019 | 65.687538959749 | | 2018 | 64.884225402062 | | 2017 | 64.06229023895 | | 2016 | 63.227563273056 | | 2015 | 62.383792350863 | | 2014 | 61.53527802119 | | 2013 | 60.683087486272 | | 2012 | 59.828549297273 | | 2011 | 58.971279497869 | | 2010 | 58.087132688887 | | 2009 | 57.14536409188 | | 2008 | 56.200553012858 | | 2007 | 55.256279857617 | | 2006 | 54.321404464236 | | 2005 | 53.37548347717 | | 2004 | 52.407711877411 | | 2003 | 51.443375772665 | | 2002 | 50.48968474058 | | 2001 | 49.549857280732 | | 2000 | 48.672795396271 | | 1999 | 47.864734598152 | | 1998 | 47.07621544187 | | 1997 | 46.298925214624 | | 1996 | 45.536451737645 | | 1995 | 44.783441084986 | | 1994 | 44.037287090387 | | 1993 | 43.299405027118 | | 1992 | 42.574515171745 | | 1991 | 41.864534585076 | | 1990 | 41.168394559519 | | 1989 | 40.514080332818 | | 1988 | 39.865106079183 | | 1987 | 39.200488052904 | | 1986 | 38.535416170831 | | 1985 | 37.864209129428 | | 1984 | 37.183065450265 | | 1983 | 36.499339536802 | | 1982 | 35.839399456955 | | 1981 | 35.104495369211 | | 1980 | 34.373668184863 | | 1979 | 33.663695840709 | | 1978 | 32.955226521236 | | 1977 | 32.418595070364 | | 1976 | 32.060788851947 | | 1975 | 31.717333507863 | | 1974 | 31.363668299628 | | 1973 | 31.029200604574 | | 1972 | 30.767999940261 | | 1971 | 30.578292083685 | | 1970 | 30.416995788907 | | 1969 | 30.267533839331 | | 1968 | 30.112359678498 | | 1967 | 29.942750413891 | | 1966 | 29.76624535815 | | 1965 | 29.619113201172 | | 1964 | 29.452841374533 | | 1963 | 28.865734784093 | | 1962 | 28.29245513538 | | 1961 | 27.628713236309 | | 1960 | 26.866921910179 |
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