| Year | Value | | 2020 | 0.74904548667883 | | 2019 | 0.73217822551127 | | 2018 | 0.74294821776192 | | 2017 | 0.7358228999582 | | 2016 | 0.73520177199925 | | 2015 | 0.73850157412421 | | 2014 | 0.74052145058795 | | 2013 | 0.73331940984946 | | 2012 | 0.77617265432129 | | 2011 | 0.77537239874467 | | 2010 | 0.78083206030222 | | 2009 | 0.78745018561538 | | 2008 | 0.78316952814421 | | 2007 | 0.7807989835004 | | 2006 | 0.83624156261358 | | 2005 | 0.85602064672591 | | 2004 | 0.82772145588544 | | 2003 | 0.86124281694082 | | 2002 | 0.87404366535479 | | 2001 | 0.89530349771985 | | 2000 | 0.93305782302448 | | 1999 | 0.94687242959641 | | 1998 | 0.99177942142057 | | 1997 | 1.0077013800127 | | 1996 | 1.0488782893835 | | 1995 | 1.0634288456462 | | 1994 | 0.7838435135522 | | 1993 | 0.81029204716018 | | 1992 | 0.87177306661414 | | 1991 | 0.79921764590275 |
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