Year % 2000 0.7991571444897791 2001 0.7651113658502932 2002 0.7303408747564197 2003 0.7114431368186002 2004 0.6806541090744552 2005 0.6429505799437657 2006 0.6009752639654505 2007 0.5724499417253537 2008 0.5581311901340602 2009 0.5522813120235616 2010 0.4933257772081582 2011 0.46772353736878586 2012 0.4456643455154136 2013 0.4108105191070944 2014 0.37642345934000854 2015 0.34653050108919226 2016 0.31897276492798904 2017 0.3007706584437034 2018 0.2927545289693596 2019 0.2806747104422992 2020 0.2755958535698916