Year Percent 1998-01-01 12.0000 1999-01-01 13.2000 2000-01-01 17.4000 2001-01-01 15.0000 2002-01-01 14.3000 2003-01-01 14.5000 2004-01-01 12.5000 2005-01-01 11.9000 2006-01-01 11.4000 2007-01-01 11.1000 2008-01-01 11.6000 2009-01-01 14.0000 2010-01-01 15.2747 2011-01-01 14.9736 2012-01-01 15.6217 2013-01-01 16.5210 2014-01-01 16.9825 2015-01-01 17.5731 2016-01-01 17.6569