| Year | Value | | 2024 | 82.700256576663 | | 2023 | 82.525056440835 | | 2022 | 82.350089735397 | | 2021 | 82.177927907927 | | 2020 | 81.950988871057 | | 2019 | 81.736367204794 | | 2018 | 81.550034164665 | | 2017 | 81.401894583223 | | 2016 | 81.30230110937 | | 2015 | 81.24656702767 | | 2014 | 81.211183161556 | | 2013 | 81.183439957458 | | 2012 | 81.151348324879 | | 2011 | 81.103142543421 | | 2010 | 81.012089225294 | | 2009 | 80.859183889392 | | 2008 | 80.66289449166 | | 2007 | 80.442561513678 | | 2006 | 80.219066099279 | | 2005 | 79.976061588297 | | 2004 | 79.692306334831 | | 2003 | 79.391380674239 | | 2002 | 79.099023480223 | | 2001 | 78.841476494974 | | 2000 | 78.629299550895 | | 1999 | 78.443930932936 | | 1998 | 78.269382308182 | | 1997 | 78.090339879087 | | 1996 | 77.89246339297 | | 1995 | 77.63564825875 | | 1994 | 77.317128542094 | | 1993 | 76.996568625591 | | 1992 | 76.735283242806 | | 1991 | 76.595384131516 | | 1990 | 76.556443707702 | | 1989 | 76.534076290494 | | 1988 | 76.517700545663 | | 1987 | 76.497942874919 | | 1986 | 76.465781906127 | | 1985 | 76.378472510978 | | 1984 | 76.218047632138 | | 1983 | 76.028293477981 | | 1982 | 75.85360553545 | | 1981 | 75.739465480008 | | 1980 | 75.676713513281 | | 1979 | 75.621370474893 | | 1978 | 75.576200338746 | | 1977 | 75.545339565296 | | 1976 | 75.532954066479 |
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