| Year | Value | | 2021 | 78.770556478405 | | 2020 | 79.084717607973 | | 2019 | 79.398878737541 | | 2018 | 79.71303986711 | | 2017 | 80.027200996678 | | 2016 | 80.341362126246 | | 2015 | 80.655523255814 | | 2014 | 80.969684385382 | | 2013 | 81.28384551495 | | 2012 | 81.598006644518 | | 2011 | 81.912167774086 | | 2010 | 82.226328903655 | | 2009 | 82.540490033223 | | 2008 | 82.854651162791 | | 2007 | 83.168812292359 | | 2006 | 83.482973421927 | | 2005 | 83.797134551495 | | 2004 | 84.111295681063 | | 2003 | 84.425456810631 | | 2002 | 84.739617940199 | | 2001 | 85.053779069767 | | 2000 | 85.367940199335 | | 1999 | 85.682101328904 | | 1998 | 85.996262458472 | | 1997 | 86.31042358804 | | 1996 | 86.624584717608 | | 1995 | 86.938745847176 | | 1994 | 87.252906976744 | | 1993 | 87.567068106312 | | 1992 | 87.88122923588 | | 1991 | 88.195390365449 | | 1990 | 88.509551495017 |
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