Year Percent 1989-01-01 3.0501400000000003 1990-01-01 7.5382700000000000 1991-01-01 9.4312300000000010 1992-01-01 6.5369500000000000 1993-01-01 15.9386000000000000 1994-01-01 14.4174000000000000 1995-01-01 10.5006000000000000 1996-01-01 11.1375000000000000 1997-01-01 18.0771000000000000 1998-01-01 13.6288000000000000 1999-01-01 22.5828000000000000 2000-01-01 27.8269999999999980 2001-01-01 21.5491000000000000 2002-01-01 16.2593000000000000 2003-01-01 16.8133000000000000 2004-01-01 20.8566000000000000 2005-01-01 26.0125000000000000 2006-01-01 28.2358000000000000 2007-01-01 33.8117000000000000 2008-01-01 27.1834000000000000 2009-01-01 25.1203000000000000 2010-01-01 35.3756000000000000 2011-01-01 28.2158000000000000 2012-01-01 28.3197000000000000 2013-01-01 26.3041000000000000 2014-01-01 21.1232000000000000 2015-01-01 21.4347000000000000 2016-01-01 19.8055000000000000 2017-01-01 21.6560000000000000