| Year | Value | | 2020 | 0.70028627703005 | | 2019 | 0.77442726125569 | | 2018 | 0.77279462629529 | | 2017 | 0.7955883489496 | | 2016 | 0.81952645888003 | | 2015 | 0.84288177908743 | | 2014 | 0.86575225089401 | | 2013 | 0.88817451461897 | | 2012 | 0.91060653680203 | | 2011 | 0.93530595594816 | | 2010 | 0.96294928806408 | | 2009 | 0.99105726555408 | | 2008 | 1.0195773414958 | | 2007 | 1.0484965607815 | | 2005 | 1.6792095168724 | | 2004 | 1.728847550223 | | 2003 | 2.0515807766209 | | 2002 | 2.774679385797 | | 2001 | 2.8245496988458 | | 2000 | 2.8035197452633 | | 1999 | 2.0657220961112 | | 1998 | 2.1479269322989 | | 1997 | 2.6109110816331 | | 1996 | 1.9603490009326 | | 1995 | 2.7679019950684 | | 1994 | 1.4328330835428 | | 1993 | 1.1786077970406 | | 1992 | 1.2093979898999 | | 1991 | 1.2316853520177 |
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