Year Percent 1997-01-01 95.85450000000000 1998-01-01 94.47160000000000 1999-01-01 92.85910000000000 2000-01-01 95.06350000000000 2001-01-01 94.34920000000000 2002-01-01 90.29700000000001 2003-01-01 90.25980000000000 2004-01-01 92.95330000000000 2005-01-01 95.57090000000000 2006-01-01 97.02890000000000 2007-01-01 97.91240000000000 2008-01-01 98.70720000000000 2009-01-01 98.94550000000000 2010-01-01 99.40890000000000 2011-01-01 99.77320000000000 2012-01-01 99.81570000000000 2013-01-01 99.83590000000000 2014-01-01 99.84810000000000 2015-01-01 99.85440000000000