Year Percent 1986-01-01 3.3750000000000000 1987-01-01 2.5000000000000000 1988-01-01 2.3000000000000000 1989-01-01 1.0781500000000000 1990-01-01 0.9114820000000000 1991-01-01 0.9114820000000000 1992-01-01 8.1016000000000000 1993-01-01 7.8109699999999990 1994-01-01 6.7122699999999990 1995-01-01 6.0018600000000000 1996-01-01 7.1453500000000000 1997-01-01 6.9216500000000000 1998-01-01 7.0608699999999995 1999-01-01 6.9390199999999990 2000-01-01 5.7854000000000000 2001-01-01 7.9849800000000000 2002-01-01 7.0715300000000000 2003-01-01 6.8202100000000000 2004-01-01 6.3618200000000000 2005-01-01 4.6793500000000000 2006-01-01 3.6052400000000002 2007-01-01 3.7813400000000000 2008-01-01 6.5759600000000000 2009-01-01 6.3597600000000000 2010-01-01 6.0225000000000000 2011-01-01 5.7683300000000010 2012-01-01 4.9508300000000010 2013-01-01 4.8766700000000000 2014-01-01 4.8866700000000000 2015-01-01 4.1675000000000000