Year Percent 2000-01-01 28.6786597031557 2001-01-01 27.9829053875554 2002-01-01 26.1135562755336 2003-01-01 27.2901726573064 2004-01-01 26.1622762586820 2005-01-01 25.4372238556901 2006-01-01 25.0253801952074 2007-01-01 23.1605502922481 2008-01-01 23.7475224591714 2009-01-01 23.5245114290813 2010-01-01 22.3830868921830 2011-01-01 21.1237408572742 2012-01-01 20.4418183043744 2013-01-01 19.6020868188424 2014-01-01 17.9349521537605 2015-01-01 18.1988103092852 2016-01-01 18.2853074327829 2017-01-01 17.2622585767269