Year Percent 2005-01-01 56.4128297109754 2006-01-01 55.0755421268761 2007-01-01 54.5561504125493 2008-01-01 54.7640911817367 2009-01-01 54.1660699712567 2010-01-01 54.3599423025785 2011-01-01 53.8388636822065 2012-01-01 52.7343873284624 2013-01-01 52.5997697298901 2014-01-01 53.4250800012631 2015-01-01 53.1541034591151 2016-01-01 53.0171548116842 2017-01-01 53.3280982676512