| Year | Value | | 2022 | 1.6074649517934 | | 2021 | 1.5552801950306 | | 2020 | 1.7380272604556 | | 2019 | 1.3344119643203 | | 2018 | 1.3692948727571 | | 2017 | 1.3627767736893 | | 2016 | 1.41128063507 | | 2015 | 1.4037175982553 | | 2014 | 1.4722723486952 | | 2013 | 1.4522614260903 | | 2012 | 1.6564617725084 | | 2011 | 1.7489693026789 | | 2010 | 1.8143477467849 | | 2009 | 1.8437612729969 | | 2008 | 1.8721824620649 | | 2007 | 1.7440584873175 | | 2006 | 2.2907131630739 | | 2005 | 2.6943633258031 |
|