Year Number 1996 1.85839378833771 1998 1.85049915313721 2000 1.79541397094727 2002 1.79115116596222 2003 1.84832954406738 2004 1.84883081912994 2005 1.84639847278595 2006 1.79479086399078 2007 1.82681655883789 2008 1.85065972805023 2009 1.92267489433289 2010 1.86188757419586 2011 1.89464735984802 2012 1.88321006298065 2013 1.87015104293823 2014 2.00416088104248 2015 1.96550953388214 2016 1.91391754150391 2017 1.8833794593811 2018 1.83372128009796 2019 1.84366428852081 2020 1.83871698379517 2021 1.78184449672699 2022 1.73179721832275