Year % 1992 94.95249 1993 95.40405 1994 95.08106 1995 95.28545 1996 96.45486 1997 96.59757 1998 96.96498 1999 97.27535 2000 97.79973 2001 96.9016 2002 96.8923 2003 97.76835 2004 98.29567 2005 98.76152 2006 98.70146 2007 98.59877 2008 98.44647 2009 98.36609 2010 98.41325 2011 98.54659 2012 97.59022 2013 98.18868 2014 98.28374 2015 98.66893 2016 98.64028 2017 98.79999