| Year | Value | | 2022 | 2.0866657905943 | | 2021 | 2.0130442340616 | | 2020 | 2.2938299705816 | | 2019 | 2.0493630178152 | | 2018 | 2.0090871203263 | | 2017 | 2.0097665085997 | | 2016 | 2.0691643663153 | | 2015 | 2.0260417420727 | | 2014 | 1.9253573857358 | | 2013 | 1.9089636493344 | | 2012 | 1.8976727839581 | | 2011 | 1.6789333031573 | | 2010 | 1.7004256219094 | | 2009 | 1.7990597956807 | | 2008 | 1.7671976129674 | | 2007 | 1.6573202363967 | | 2006 | 1.3875620658765 | | 2005 | 1.4509199321799 | | 2004 | 1.6996892247017 | | 2003 | 1.7430492952598 | | 2002 | 1.6671295009216 | | 2001 | 1.5022144619276 | | 2000 | 1.3763271152777 | | 1999 | 1.2871133644757 | | 1998 | 1.0674917182745 | | 1997 | 1.0467724867254 | | 1996 | 0.87359607383783 | | 1995 | 0.95809832700849 | | 1994 | 1.0416302736588 | | 1993 | 0.76175196094564 |
|