Year Percent 1995-01-01 33.66 1996-01-01 36.79 1997-01-01 41.94 1998-01-01 45.13 1999-01-01 51.75 2000-01-01 52.47 2001-01-01 53.48 2002-01-01 53.80 2003-01-01 57.72 2004-01-01 58.11 2005-01-01 59.63 2006-01-01 58.60 2007-01-01 57.44 2008-01-01 54.28 2009-01-01 46.76 2010-01-01 46.42 2011-01-01 45.13 2012-01-01 46.28 2013-01-01 47.28 2014-01-01 47.61 2015-01-01 47.82