Year Percent 1990-01-01 2.4532300000000000 1991-01-01 2.5673500000000000 1992-01-01 2.7180800000000000 1993-01-01 3.1882800000000000 1994-01-01 3.0001700000000002 1995-01-01 3.1201700000000000 1996-01-01 3.5077300000000005 1997-01-01 3.7050000000000000 1998-01-01 4.5573800000000000 1999-01-01 4.5282400000000000 2000-01-01 4.6742099999999995 2001-01-01 4.9367700000000000 2002-01-01 5.2099199999999990 2003-01-01 5.5494600000000000 2004-01-01 5.8794100000000000 2005-01-01 6.3112900000000005 2006-01-01 6.5144800000000010 2007-01-01 5.8525000000000000 2008-01-01 6.2380600000000000 2009-01-01 6.2498400000000000 2010-01-01 6.4639700000000000 2011-01-01 6.7619800000000000 2012-01-01 6.9268000000000000 2013-01-01 7.0563699999999990 2014-01-01 7.2999600000000004 2015-01-01 7.4308600000000010 2016-01-01 7.3278399999999990