| Year | Value | | 2020 | 0.87134953258228 | | 2019 | 0.86001817015274 | | 2018 | 0.85629566365073 | | 2017 | 0.85597402835047 | | 2016 | 0.861499739831 | | 2015 | 0.86798561700733 | | 2014 | 0.86612695697597 | | 2013 | 0.91697971269712 | | 2012 | 0.9147308364208 | | 2011 | 0.91557902924173 | | 2010 | 0.95058314223312 | | 2009 | 0.95197711954139 | | 2008 | 0.96327116173915 | | 2007 | 0.98630169120529 | | 2006 | 1.0146185045849 | | 2005 | 1.0378485927032 | | 2004 | 1.0774118979477 | | 2003 | 1.13525901644 | | 2002 | 1.3248724335607 | | 2001 | 1.1843857467698 | | 2000 | 1.3255066677974 | | 1999 | 1.4794574239671 | | 1998 | 1.5493235905153 | | 1997 | 1.5937633895081 | | 1996 | 1.6790806417883 | | 1995 | 1.7024793928049 | | 1994 | 1.297632162465 | | 1993 | 1.2692757251391 | | 1992 | 1.2500466399977 | | 1991 | 1.5752777195409 |
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