| Year | Value | | 2020 | 0.49533526271922 | | 2019 | 0.49470696527619 | | 2018 | 0.48491431564043 | | 2017 | 0.50565252098121 | | 2016 | 0.54767921781883 | | 2015 | 0.57333033083232 | | 2014 | 0.6003431729114 | | 2013 | 0.6034257744198 | | 2012 | 0.59894126684435 | | 2011 | 0.56976997918348 | | 2010 | 0.64488790970184 | | 2009 | 0.643037852851 | | 2008 | 1.0278513452861 | | 2007 | 1.025727642642 | | 2006 | 1.0282011586456 | | 2005 | 0.7258514410225 | | 2004 | 0.72523253199743 | | 2003 | 0.79492530839964 | | 2002 | 0.7912363084748 | | 2001 | 0.75312149503767 | | 2000 | 0.76409188730696 | | 1999 | 0.9436359270856 | | 1998 | 1.1333193051235 | | 1997 | 1.1579186324594 | | 1996 | 1.1637226958467 | | 1995 | 1.1849991282559 | | 1994 | 1.0089468360688 | | 1993 | 0.93138744648403 | | 1992 | 0.95750294175681 | | 1991 | 1.0331770366072 |
|