Year Number 1996 -2.06191730499268 1998 -2.31805849075317 2000 -2.03817391395569 2002 -1.5761798620224 2003 -1.0073858499527 2004 -1.0631206035614 2005 -0.885178327560425 2006 -0.539453446865082 2007 -0.666658759117126 2008 -0.361787378787994 2009 -0.34759184718132 2010 -0.226182341575623 2011 -0.369237810373306 2012 -0.389322549104691 2013 -0.39123347401619 2014 -0.333232045173645 2015 -0.50538581609726 2016 -0.321580082178116 2017 -0.38913482427597 2018 -0.347750902175903 2019 -0.370094686746597 2020 -0.600726008415222 2021 -0.709369480609894 2022 -0.646240890026093