Year scale 0 - 100 2004 78.6928104901961 2005 80.71888882352941 2006 80.915 2007 80.71190932038837 2008 80.80899640776698 2009 80.85707923809528 2010 81.82533380952378 2011 82.2222221904762 2012 81.65079342857143 2013 79.98442367601243 2014 79.11526479750775 2015 80.9259564814815 2016 81.45064166666668 2017 83.11729722222223 2018 83.73459074074079 2019 82.80866296296298 2020 81.38891018518525