Year Percent 1990-01-01 1.7813299999999999 1991-01-01 1.9455700000000000 1992-01-01 2.0738000000000000 1993-01-01 2.1448800000000000 1994-01-01 2.2253000000000000 1995-01-01 2.4922600000000000 1996-01-01 2.7287400000000000 1997-01-01 2.9982800000000000 1998-01-01 2.6854900000000000 1999-01-01 2.4848500000000000 2000-01-01 2.1148200000000000 2001-01-01 2.6339500000000000 2002-01-01 2.6101799999999997 2003-01-01 2.5508200000000000 2004-01-01 2.5593800000000000 2005-01-01 2.6847700000000000 2006-01-01 2.9296000000000000 2007-01-01 3.1175200000000003 2008-01-01 3.2482700000000000 2009-01-01 3.6536900000000000 2010-01-01 3.9717300000000004 2011-01-01 4.4299300000000010 2012-01-01 4.8040100000000000 2013-01-01 3.6380800000000004 2014-01-01 4.9917400000000000 2015-01-01 4.9730500000000000 2016-01-01 4.7474900000000000