Year Percent 2001-01-01 11.0000 2002-01-01 15.0000 2003-01-01 18.0000 2004-01-01 18.0000 2005-01-01 18.0000 2006-01-01 18.0000 2007-01-01 18.0000 2008-01-01 18.0000 2009-01-01 30.4146 2010-01-01 28.2438 2011-01-01 25.4396 2012-01-01 28.0086 2013-01-01 26.9542 2014-01-01 27.5123 2015-01-01 28.0161