Year % 1992 82.66465 1993 84.32182 1996 78.1262 1998 80.72413 1999 80.21849 2000 81.29553 2001 85.02698 2002 86.75904 2003 85.33895 2004 85.2203 2005 83.35547 2006 83.33333 2007 83.90961 2008 85.14532 2009 84.89577 2010 84.6216 2011 86.25994 2012 88.27274 2013 91.64324 2014 90.20914 2015 89.61929 2016 88.99404 2017 87.56268