Year Percent 1976-01-01 40.353600000000000 1977-01-01 43.135300000000000 1978-01-01 32.931900000000000 1979-01-01 23.756900000000000 1980-01-01 26.874500000000000 1981-01-01 26.719100000000000 1982-01-01 24.758300000000000 1983-01-01 24.287500000000000 1984-01-01 22.155200000000000 1985-01-01 23.090300000000000 1986-01-01 24.131900000000000 1987-01-01 21.808800000000000 1988-01-01 17.639800000000000 1989-01-01 15.158800000000000 1990-01-01 14.305700000000000 1991-01-01 15.085100000000000 1992-01-01 17.270700000000000 1993-01-01 20.407200000000000 1994-01-01 21.741800000000000 1995-01-01 19.055900000000000 1996-01-01 16.759400000000000 1997-01-01 12.472500000000000 1998-01-01 11.933300000000000 1999-01-01 12.277999999999999 2000-01-01 13.618000000000000 2001-01-01 15.275000000000000 2002-01-01 15.562800000000000 2003-01-01 12.001700000000000 2004-01-01 8.156480000000000 2005-01-01 10.311300000000000 2006-01-01 8.376570000000000 2007-01-01 7.189089999999999 2008-01-01 9.092450000000000 2009-01-01 12.647700000000000 2010-01-01 12.365800000000000 2011-01-01 9.724039999999999 2012-01-01 10.069400000000000 2013-01-01 11.109200000000000 2014-01-01 11.185100000000000 2015-01-01 10.467400000000000 2016-01-01 11.349900000000000