Year Number 1996 0.478682190179825 1998 0.562503397464752 2000 0.5645592212677 2002 0.981545209884644 2003 0.76597386598587 2004 0.770029485225677 2005 0.500354409217834 2006 0.426627278327942 2007 0.364861726760864 2008 0.412061005830765 2009 0.304186642169952 2010 0.298077821731567 2011 0.078883208334446 2012 -0.197435706853867 2013 -0.195034772157669 2014 -0.246068090200424 2015 -0.254954397678375 2016 -0.297969162464142 2017 -0.359839290380478 2018 -0.316699147224426 2019 -0.159434482455254 2020 -0.0917352288961411 2021 -0.0562744364142418 2022 0.127030700445175