Year Number 1996 0.231270432472229 1998 0.00787538941949606 2000 0.248432531952858 2002 0.263644099235535 2003 0.316652774810791 2004 0.355422109365463 2005 0.424785822629929 2006 0.474477261304855 2007 0.45094159245491 2008 0.524226605892181 2009 0.356679856777191 2010 0.349292427301407 2011 0.280382126569748 2012 0.307248294353485 2013 0.370564639568329 2014 0.544822037220001 2015 0.634750008583069 2016 0.6731316447258 2017 0.638509929180145 2018 0.640438854694366 2019 0.610411107540131 2020 0.59608781337738 2021 0.392701923847198 2022 0.49952158331871