Year % 1970 65.41314 1971 72.12967 1972 79.959 1973 80.28842 1974 80.99994 1992 92.06165 1993 91.19794 1994 92.07209 1995 92.47279 1996 92.84183 1997 93.58922 1998 94.54215 1999 94.96687 2000 95.21528 2001 96.38089 2002 95.90754 2003 95.31977 2004 95.34061 2005 95.19009 2006 95.39916 2007 95.24317 2008 95.80849 2009 95.61433 2010 95.70008 2011 95.52865 2012 95.71331 2013 95.77655 2014 95.56799 2015 95.6832 2016 95.82466 2017 96.00999