Year Percent 1997-01-01 10.5190000000000000 1998-01-01 7.7862399999999990 1999-01-01 7.5193400000000000 2000-01-01 5.3876200000000000 2001-01-01 4.4052900000000000 2002-01-01 3.6171100000000000 2003-01-01 3.9686100000000000 2004-01-01 4.2773800000000000 2005-01-01 6.3223699999999990 2006-01-01 6.0397200000000000 2007-01-01 5.8163000000000000 2008-01-01 5.7717000000000000 2009-01-01 4.2459000000000000 2010-01-01 4.3613500000000000 2011-01-01 3.9513599999999998 2012-01-01 3.7131800000000004 2013-01-01 3.4054300000000004 2014-01-01 2.8904500000000000 2015-01-01 2.8945500000000000 2016-01-01 2.3535400000000000