Year Number 1996 -0.668952643871307 1998 -0.752315282821655 2000 -0.439044535160065 2002 -0.35481521487236 2003 -0.459642589092255 2004 -0.713360965251923 2005 -0.999740839004517 2006 -1.8038626909256 2007 -2.11909532546997 2008 -1.87660884857178 2009 -1.5616968870163 2010 -1.62501502037048 2011 -1.55828750133514 2012 -1.66481232643127 2013 -1.69035339355469 2014 -1.69794130325317 2015 -1.69836449623108 2016 -1.61568403244019 2017 -1.62222683429718 2018 -1.62153577804565 2019 -1.67229104042053 2020 -1.62113451957703 2021 -1.48194456100464 2022 -1.47351241111755