Year % 1979 92.36679 1980 92.62141 1981 93.47987 1982 94.66492 1983 94.78293 1984 94.41633 2002 100 2003 99.76569 2004 100 2005 100 2006 99.66786 2007 99.94425 2008 99.70184 2010 99.56538 2011 99.90408 2012 99.91875 2013 99.47115 2014 99.58346 2015 99.23659 2016 99.09205 2017 99.8591