Year Percent 1996-01-01 13.70 1997-01-01 12.13 1998-01-01 11.99 1999-01-01 7.92 2000-01-01 9.69 2001-01-01 6.62 2002-01-01 3.03 2003-01-01 2.45 2004-01-01 2.37 2005-01-01 4.53 2006-01-01 5.36 2007-01-01 5.93 2008-01-01 8.24 2009-01-01 0.45 2010-01-01 3.13 2011-01-01 5.23 2012-01-01 4.99 2013-01-01 4.50 2014-01-01 3.00 2015-01-01 3.35 2016-01-01 3.48 2017-01-01 2.50