Year Percent 1995-01-01 12.75 1996-01-01 15.56 1997-01-01 19.40 1998-01-01 21.40 1999-01-01 32.59 2000-01-01 29.84 2001-01-01 25.39 2002-01-01 24.63 2003-01-01 25.77 2004-01-01 24.55 2005-01-01 26.85 2006-01-01 27.54 2007-01-01 25.50 2008-01-01 22.07 2009-01-01 27.01 2010-01-01 27.78 2011-01-01 25.97 2012-01-01 28.18 2013-01-01 30.24 2014-01-01 32.08 2015-01-01 33.53 2016-01-01 33.93