Year Number 1996 -0.988058924674988 1998 -0.809740364551544 2000 -0.294286817312241 2002 -0.0953808054327965 2003 0.120704226195812 2004 0.355680614709854 2005 0.448557078838348 2006 0.358128875494003 2007 0.747057616710663 2008 0.808881163597107 2009 0.831896722316742 2010 0.0280884467065334 2011 -1.28737926483154 2012 -1.5869597196579 2013 -1.84407651424408 2014 -2.35340714454651 2015 -2.18965125083923 2016 -2.27473783493042 2017 -2.35357475280762 2018 -2.43496870994568 2019 -2.56577134132385 2020 -2.46227836608887 2021 -2.30834579467773 2022 -2.19796347618103