Year Percent 1991-01-01 6.5939399999999990 1992-01-01 5.6474699999999990 1993-01-01 6.5689400000000000 1994-01-01 6.7478800000000000 1995-01-01 6.3182199999999990 1996-01-01 6.4663600000000000 1997-01-01 6.7115500000000000 1998-01-01 6.9314800000000005 1999-01-01 6.9314800000000005 2000-01-01 8.6633300000000000 2001-01-01 8.7619800000000000 2002-01-01 9.5332300000000000 2003-01-01 11.6377000000000000 2004-01-01 11.2068000000000000 2005-01-01 10.7122000000000000 2006-01-01 13.2557000000000000 2007-01-01 13.9002000000000000 2008-01-01 13.1429000000000000 2009-01-01 15.7724000000000000 2010-01-01 19.8335000000000000 2011-01-01 25.2572000000000000 2012-01-01 23.3411000000000000 2013-01-01 21.5786000000000000 2014-01-01 22.9062000000000000 2015-01-01 24.9842000000000000 2016-01-01 24.7682000000000000