Year Number 2004 0.393849045038223 2005 0.281408816576004 2006 0.315948367118835 2007 0.318616777658463 2008 0.327212035655975 2009 0.307390600442886 2010 0.297930240631104 2011 0.302551865577698 2012 0.297558695077896 2013 0.29543325304985 2014 0.334085315465927 2015 0.295054972171783 2016 0.295681953430176 2017 0.288345098495483 2018 0.246614575386047 2019 0.252823859453201 2020 0.255439341068268 2021 0.320136547088623 2022 0.331636041402817