Year Percent 2000-01-01 9.65 2001-01-01 8.59 2002-01-01 7.10 2003-01-01 9.34 2004-01-01 10.14 2005-01-01 13.67 2006-01-01 17.39 2007-01-01 19.55 2008-01-01 12.31 2009-01-01 18.63 2010-01-01 21.04 2011-01-01 18.97 2012-01-01 20.65 2013-01-01 23.79 2014-01-01 28.97 2015-01-01 30.89 2016-01-01 33.80