| Year | Value | | 2020 | 1.0065220694481 | | 2019 | 0.98783106113192 | | 2018 | 0.99667710713754 | | 2017 | 0.99485525908231 | | 2016 | 1.4361841685467 | | 2015 | 1.4142931618349 | | 2014 | 1.4927966350338 | | 2013 | 1.5096889511377 | | 2012 | 1.6768272867895 | | 2011 | 1.6633638854412 | | 2010 | 1.6449381650456 | | 2009 | 1.6582636318596 | | 2008 | 1.6438585804721 | | 2007 | 1.6443011593588 | | 2006 | 1.6544807793877 | | 2005 | 1.7017987463782 | | 2004 | 1.6792995512395 | | 2003 | 1.701478687877 | | 2002 | 1.6605549020965 | | 2001 | 1.6869114787579 | | 2000 | 1.7294782594072 | | 1999 | 1.7520060566037 | | 1998 | 1.8444257160958 | | 1997 | 2.0692552044247 | | 1996 | 2.166329080385 | | 1995 | 2.1684931703933 | | 1994 | 2.5519942684719 | | 1993 | 1.4250620635486 | | 1992 | 1.6709111290409 | | 1991 | 1.7759374110095 |
|