Year Percent 1995-01-01 31.66 1996-01-01 30.47 1997-01-01 31.77 1998-01-01 33.37 1999-01-01 36.64 2000-01-01 31.77 2001-01-01 32.82 2002-01-01 33.86 2003-01-01 36.38 2004-01-01 36.72 2005-01-01 37.39 2006-01-01 37.06 2007-01-01 38.65 2008-01-01 35.08 2009-01-01 40.09 2010-01-01 40.62 2011-01-01 39.40 2012-01-01 40.37 2013-01-01 42.56 2014-01-01 45.67 2015-01-01 49.02 2016-01-01 52.00