Year Percent 1999-01-01 2.17 2000-01-01 2.20 2001-01-01 2.25 2002-01-01 2.40 2003-01-01 2.20 2004-01-01 2.32 2005-01-01 2.63 2006-01-01 3.30 2007-01-01 3.41 2008-01-01 3.50 2009-01-01 3.82 2010-01-01 3.91 2011-01-01 3.68 2012-01-01 3.78 2013-01-01 4.00 2014-01-01 4.23 2015-01-01 4.31 2016-01-01 4.27