Year scale 0 - 100 2004 77.12121181818182 2005 78.7878790909091 2006 78.03030272727273 2007 78.18181818181816 2008 77.57575772727274 2009 78.18181818181819 2010 78.93939409090908 2011 79.99999909090907 2012 78.6363640909091 2013 77.46376811594202 2014 75.28985507246377 2015 79.13046956521738 2016 79.71017826086955 2017 79.56522608695651 2018 81.15945217391304 2019 79.8551 2020 79.42032173913043