Year Number 1996 0.480888694524765 1998 0.453148931264877 2000 0.461006760597229 2002 0.427986711263657 2003 0.395839601755142 2004 0.393849045038223 2005 0.340958386659622 2006 0.398741275072098 2007 0.308911830186844 2008 0.297634989023209 2009 0.244014859199524 2010 0.25070509314537 2011 0.250233918428421 2012 0.269011974334717 2013 0.260900974273682 2014 0.256683349609375 2015 0.250381499528885 2016 0.299287557601929 2017 0.246166571974754 2018 0.281422942876816 2019 0.284793734550476 2020 0.26276308298111 2021 0.30851623415947 2022 0.307066679000854