Year Percent 2000-01-01 2.27 2001-01-01 2.45 2002-01-01 2.52 2003-01-01 2.50 2004-01-01 3.25 2005-01-01 3.77 2006-01-01 9.79 2007-01-01 11.85 2008-01-01 9.82 2009-01-01 13.33 2010-01-01 14.07 2011-01-01 13.52 2012-01-01 13.95 2013-01-01 13.88 2014-01-01 14.52 2015-01-01 17.50 2016-01-01 17.90