| Year | Value | | 2023 | 81.268991259332 | | 2022 | 81.046499229375 | | 2021 | 80.782602974741 | | 2020 | 78.476186761702 | | 2019 | 79.409257135438 | | 2018 | 78.138024428404 | | 2017 | 78.024955660259 | | 2016 | 78.5259417393 | | 2015 | 79.118499728212 | | 2014 | 81.149524712205 | | 2013 | 84.009992227181 | | 2012 | 83.760637645616 | | 2011 | 83.574674768484 | | 2010 | 83.866176262555 | | 2009 | 84.051184290608 | | 2008 | 83.961448104352 | | 2007 | 83.676772802233 | | 2006 | 83.358072930878 | | 2005 | 83.139809308034 | | 2004 | 83.106402350702 | | 2003 | 83.08483625236 | | 2002 | 83.171951479038 | | 2001 | 83.214103219213 | | 2000 | 83.16736916574 | | 1999 | 83.206384615843 | | 1998 | 83.255272814057 | | 1997 | 83.107214458841 | | 1996 | 83.036190818866 | | 1995 | 82.998057505067 | | 1994 | 82.985234672916 | | 1993 | 82.991287336751 | | 1992 | 82.994714638995 | | 1991 | 82.991163054136 |
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