Year Percent 2005-01-01 27.6565342096048 2006-01-01 28.6390497433382 2007-01-01 29.0021615641700 2008-01-01 29.0947099140649 2009-01-01 29.3698214572537 2010-01-01 29.3744491938895 2011-01-01 29.7226494691796 2012-01-01 30.7661506168503 2013-01-01 30.8210006289766 2014-01-01 30.2485605096661 2015-01-01 30.8190272505525 2016-01-01 31.1838192432890 2017-01-01 31.1924533972569