Year Percent 1999-01-01 2.1923600000000000 2000-01-01 2.2396599999999998 2001-01-01 3.6003100000000000 2002-01-01 7.9130600000000010 2003-01-01 13.5989000000000000 2004-01-01 16.6863000000000000 2005-01-01 18.3454000000000000 2006-01-01 23.3630000000000030 2007-01-01 25.5833000000000000 2008-01-01 15.7124000000000000 2009-01-01 23.6416000000000000 2010-01-01 20.2499000000000000 2011-01-01 14.9029000000000000 2012-01-01 15.0544000000000000 2013-01-01 22.4840000000000000 2014-01-01 17.4991000000000000 2015-01-01 22.9260000000000000 2016-01-01 22.3009000000000000