Year Percent 1985-01-01 12.4888000000000000 1986-01-01 10.5651000000000000 1987-01-01 7.8751200000000000 1988-01-01 8.1981100000000000 1989-01-01 10.1677000000000000 1990-01-01 8.5174800000000000 1991-01-01 6.6088000000000000 1992-01-01 5.2933300000000000 1993-01-01 4.9720699999999995 1994-01-01 4.6317300000000000 1995-01-01 5.2534600000000000 1996-01-01 4.5261400000000000 1997-01-01 3.1992000000000000 1998-01-01 5.2776600000000000 1999-01-01 4.2115599999999995 2000-01-01 3.4206500000000000 2001-01-01 3.2225200000000003 2002-01-01 4.0780699999999990 2003-01-01 4.3778300000000000 2004-01-01 4.4260699999999990 2005-01-01 4.4639200000000000 2006-01-01 4.5423300000000010 2007-01-01 4.9583900000000005 2008-01-01 4.9691300000000010 2009-01-01 7.4643100000000000 2010-01-01 8.9478600000000000 2011-01-01 8.7397500000000000 2012-01-01 10.1597000000000000 2013-01-01 13.7459000000000000 2014-01-01 13.4101000000000000 2015-01-01 17.0566000000000000 2016-01-01 17.8359000000000000