| Year | Value | | 2020 | 0.46446926258538 | | 2019 | 0.50053856023933 | | 2018 | 0.61235582422316 | | 2017 | 0.62913731511719 | | 2016 | 0.67638053168713 | | 2015 | 0.72851574986918 | | 2014 | 0.75518294507691 | | 2013 | 0.75573603651717 | | 2012 | 0.62513133866887 | | 2011 | 0.69820660353758 | | 2010 | 0.73020695940196 | | 2009 | 0.82301953238266 | | 2008 | 0.81635164912453 | | 2007 | 0.82472587380764 | | 2006 | 0.86080688163454 | | 2005 | 0.79970968377102 | | 2004 | 0.80252545844824 | | 2003 | 0.92676342864308 | | 2002 | 0.898043845158 | | 2001 | 0.91293242932941 | | 2000 | 0.88983986278805 | | 1999 | 0.95503467976829 | | 1998 | 1.0235481660218 | | 1997 | 1.051047820193 | | 1996 | 1.1009879404962 | | 1995 | 1.1232676808758 | | 1994 | 1.2704390877193 | | 1993 | 1.7047117746391 | | 1992 | 1.935701864669 | | 1991 | 2.5026352005305 |
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