Year Percent 1975-01-01 9.2321 1976-01-01 8.4471 1977-01-01 5.8757 1978-01-01 6.6071 1979-01-01 13.2143 1980-01-01 18.9643 1981-01-01 12.8214 1982-01-01 10.3757 1983-01-01 9.0671 1984-01-01 10.1614 1985-01-01 9.8393 1986-01-01 8.1607 1987-01-01 8.5000 1988-01-01 10.3514 1989-01-01 12.0625 1990-01-01 11.6161 1991-01-01 7.4018 1992-01-01 6.7946 1993-01-01 3.7857 1994-01-01 5.5357 1995-01-01 5.7086 1996-01-01 3.0100 1997-01-01 4.3357 1998-01-01 5.1129 1999-01-01 4.7586 2000-01-01 5.8000 2001-01-01 2.2444 2002-01-01 2.7439 2003-01-01 2.7481 2004-01-01 2.4999 2005-01-01 3.2437 2006-01-01 4.2482 2007-01-01 4.2597 2008-01-01 1.5017 2009-01-01 0.2455 2010-01-01 0.9924 2011-01-01 0.9998 2012-01-01 0.9982 2013-01-01 1.0012 2014-01-01 1.0114 2015-01-01 0.5242 2016-01-01 0.4936 2017-01-01 0.9970