Year Number 1996 -1.18347084522247 1998 -1.11872601509094 2000 -0.997799515724182 2002 -1.14361846446991 2003 -0.907567977905273 2004 -0.910640358924866 2005 -0.980864763259888 2006 -1.08017063140869 2007 -0.955795526504517 2008 -0.823480367660522 2009 -0.943409562110901 2010 -1.00942170619965 2011 -1.07831406593323 2012 -0.980967283248901 2013 -1.2608003616333 2014 -1.3894624710083 2015 -1.52139818668365 2016 -1.69688093662262 2017 -1.68153071403503 2018 -1.69031953811646 2019 -1.76251399517059 2020 -1.88033723831177 2021 -1.80397236347198 2022 -1.80244541168213