Year Percent 1995-01-01 38.6558669665528 1996-01-01 39.6355178824823 1997-01-01 40.7899994897076 1998-01-01 39.8897571517741 1999-01-01 38.4430841089922 2000-01-01 37.1266762871308 2001-01-01 36.7689469795196 2002-01-01 34.7413399480675 2003-01-01 33.5220928706829 2004-01-01 33.9339297223143 2005-01-01 34.3001345916135 2006-01-01 33.7757725412536 2007-01-01 33.5105865251864 2008-01-01 33.2032923963111 2009-01-01 34.7453834462610 2010-01-01 35.1785770697631 2011-01-01 35.5451228012606 2012-01-01 36.3153021867749 2013-01-01 36.1720547744565 2014-01-01 35.3699933446398 2015-01-01 35.5743788481337 2016-01-01 35.9745381260430 2017-01-01 36.0176087810104