Year Number 1996 0.262547045946121 1998 0.263467073440552 2000 0.321114897727966 2002 0.154225796461105 2003 0.317870795726776 2004 0.148958027362823 2005 0.0242274515330791 2006 0.20851244032383 2007 0.158262476325035 2008 0.0998212322592735 2009 0.0596117079257965 2010 -0.0639763623476028 2011 -0.3537417948246 2012 -0.721316933631897 2013 -0.902563273906708 2014 -0.851661503314972 2015 -0.960177004337311 2016 -1.13972234725952 2017 -1.02349030971527 2018 -0.868218719959259 2019 -0.877072870731354 2020 -0.59433114528656 2021 -0.756551444530487 2022 -0.596295177936554