| Year | Value | | 2020 | 0.57019322287523 | | 2019 | 0.64420337299391 | | 2018 | 0.62797271986857 | | 2017 | 0.6086406144687 | | 2016 | 0.62652850387293 | | 2015 | 0.68347037747822 | | 2014 | 0.68901803005567 | | 2013 | 0.71257991126251 | | 2012 | 0.97494538844697 | | 2011 | 0.99444512021022 | | 2010 | 0.93952176515249 | | 2009 | 0.82716455943568 | | 2008 | 0.75419840820866 | | 2007 | 0.66447050454627 | | 2005 | 0.61300170574578 | | 2004 | 0.60063633201603 | | 2003 | 0.8286937923438 | | 2002 | 0.82205026030934 | | 2001 | 0.83662053053033 | | 2000 | 1.0395398343802 | | 1999 | 1.0448700821968 | | 1998 | 1.0794989324059 | | 1997 | 1.0901357394542 | | 1996 | 1.1025235929794 | | 1995 | 1.1088173152912 | | 1994 | 0.73923611565734 | | 1993 | 0.78623336870533 | | 1992 | 0.7855079842943 | | 1991 | 0.89242084088423 |
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