| Year | Value | | 2021 | 9.1139740339905 | | 2020 | 9.1296947690911 | | 2019 | 9.1554970435019 | | 2018 | 9.1237371960589 | | 2017 | 9.1386964692638 | | 2016 | 9.1588343838163 | | 2015 | 9.1715842033591 | | 2014 | 9.27972023158 | | 2013 | 9.3049618049102 | | 2012 | 9.3942175309775 | | 2011 | 9.4835122725781 | | 2010 | 9.5711781817514 | | 2009 | 9.6594753925381 | | 2008 | 9.7484442629832 | | 2007 | 9.8375169730999 | | 2006 | 9.9300217964896 | | 2005 | 10.019525110761 | | 2004 | 10.108912867412 | | 2003 | 10.197831039491 | | 2002 | 10.286503437628 | | 2001 | 10.279621298843 | | 2000 | 10.276054270412 | | 1999 | 10.528913963329 | | 1998 | 10.526563234603 | | 1997 | 10.524212505877 | | 1996 | 10.521861777151 | | 1995 | 10.519511048425 | | 1994 | 10.503055947344 | | 1993 | 10.510108133521 | | 1992 | 10.517160319699 |
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