Year Number 1996 0.242076978087425 1998 0.332852572202683 2000 0.301593601703644 2002 0.472238034009933 2003 0.442828863859177 2004 0.38860946893692 2005 0.457679510116577 2006 0.500075697898865 2007 0.537074029445648 2008 0.5689857006073 2009 0.521999180316925 2010 0.571348905563354 2011 0.513676166534424 2012 0.477906197309494 2013 0.417426258325577 2014 0.471947550773621 2015 0.458866268396378 2016 0.451864898204803 2017 0.449006587266922 2018 0.37796550989151 2019 0.302083343267441 2020 0.28843942284584 2021 0.255604922771454 2022 0.214864358305931