| Year | Value | | 2021 | 8.6921083463498 | | 2020 | 8.7182152395866 | | 2019 | 8.7414538087729 | | 2018 | 8.767757210877 | | 2017 | 8.794326890187 | | 2016 | 8.8199736666096 | | 2015 | 8.8452459775896 | | 2014 | 8.8751971156394 | | 2013 | 8.9003422226112 | | 2012 | 8.9240261072403 | | 2011 | 8.9496163850208 | | 2010 | 8.9774837923361 | | 2009 | 9.0032516174664 | | 2008 | 9.0302546656054 | | 2007 | 9.0582202286878 | | 2006 | 9.0864741522537 | | 2005 | 9.1109855799934 | | 2004 | 9.1403207692014 | | 2003 | 10.98 | | 2002 | 11.011287128713 | | 2001 | 11.042574257426 | | 2000 | 11.073861386139 | | 1999 | 11.105148514851 | | 1998 | 11.136435643564 | | 1997 | 11.167722772277 | | 1996 | 11.19900990099 | | 1995 | 11.230297029703 | | 1994 | 11.261584158416 | | 1993 | 11.292871287129 |
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