Year Number 1996 1.62873435020447 1998 1.73309910297394 2000 1.66714358329773 2002 1.65189230442047 2003 1.6673995256424 2004 1.60760021209717 2005 1.55816102027893 2006 1.77239453792572 2007 1.72019219398499 2008 1.69664943218231 2009 1.73159778118134 2010 1.77469253540039 2011 1.65874373912811 2012 1.72941386699677 2013 1.68943524360657 2014 1.87480342388153 2015 1.77103567123413 2016 1.64045774936676 2017 1.64431941509247 2018 1.60294651985168 2019 1.56944584846497 2020 1.46293222904205 2021 1.3965802192688 2022 1.41549122333527