Year Number 1996 0.687231183052063 1998 0.839022397994995 2000 0.566399753093719 2002 0.566648781299591 2003 0.613744556903839 2004 0.574701726436615 2005 0.613131701946259 2006 0.608323812484741 2007 0.545622229576111 2008 0.533641874790192 2009 0.554204344749451 2010 0.523346245288849 2011 0.520742893218994 2012 0.501116394996643 2013 0.482290118932724 2014 0.473105400800705 2015 0.480548501014709 2016 0.558559715747833 2017 0.554904460906982 2018 0.546445190906525 2019 0.597126185894012 2020 0.642406761646271 2021 0.664211511611938 2022 0.646616280078888