Year Percent 1991-01-01 2.5328800000000000 1992-01-01 3.6366400000000003 1993-01-01 3.1719000000000000 1994-01-01 2.5747100000000000 1995-01-01 2.3552200000000000 1996-01-01 2.3127000000000000 1997-01-01 2.1641800000000000 1998-01-01 2.1624700000000000 1999-01-01 2.0063299999999997 2000-01-01 2.0076900000000000 2001-01-01 2.0942800000000000 2002-01-01 2.1606200000000000 2003-01-01 2.2200100000000000 2004-01-01 2.3197500000000000 2005-01-01 2.3962600000000000 2006-01-01 2.3627400000000000 2007-01-01 2.3004100000000000 2008-01-01 2.3135400000000000 2009-01-01 2.5378300000000000 2010-01-01 2.5458300000000000 2011-01-01 2.5001200000000000 2012-01-01 2.4640600000000000 2013-01-01 2.3417600000000000 2014-01-01 2.2451200000000000 2015-01-01 2.1503400000000004 2016-01-01 2.1604900000000002