Year Percent 1998-01-01 4.200 1999-01-01 3.300 2000-01-01 3.100 2001-01-01 2.200 2002-01-01 3.600 2003-01-01 4.700 2004-01-01 7.100 2005-01-01 5.800 2006-01-01 6.200 2007-01-01 4.700 2008-01-01 6.050 2009-01-01 6.150 2010-01-01 5.075 2011-01-01 6.250 2012-01-01 5.875 2013-01-01 6.400 2014-01-01 5.800 2015-01-01 7.350 2016-01-01 6.625 2017-01-01 5.500