Year Percent 1965-01-01 9.0899000000000000 1966-01-01 8.6007800000000000 1967-01-01 9.2830600000000000 1968-01-01 9.9866900000000000 1969-01-01 10.6199000000000000 1970-01-01 6.1252600000000000 1971-01-01 5.9637100000000000 1972-01-01 6.6119900000000000 1973-01-01 7.6877699999999995 1974-01-01 8.4190700000000000 1975-01-01 8.2757200000000000 1976-01-01 7.8208899999999995 1977-01-01 8.1710700000000000 1978-01-01 9.0598200000000000 1979-01-01 9.4503700000000000 1980-01-01 8.2636800000000000 1981-01-01 9.1714399999999990 1982-01-01 9.7123500000000000 1983-01-01 9.0022899999999990 1984-01-01 9.4440900000000000 1985-01-01 9.4574000000000000 1986-01-01 9.3616900000000000 1987-01-01 10.4464000000000000 1988-01-01 9.9919300000000000 1989-01-01 9.0035899999999990 1990-01-01 9.0647000000000000 1991-01-01 7.9261500000000000 1992-01-01 9.0307600000000000 1993-01-01 7.9273600000000000 1994-01-01 9.0741600000000010 1995-01-01 6.9601000000000000 1996-01-01 6.5178900000000000 1997-01-01 6.0817400000000000 1998-01-01 6.2023300000000000 1999-01-01 6.4995000000000000 2000-01-01 6.5931800000000000 2001-01-01 7.5565700000000000 2002-01-01 7.5932600000000010 2003-01-01 7.9416800000000000 2004-01-01 8.2863000000000000 2005-01-01 8.8935000000000000 2006-01-01 8.2343700000000000 2007-01-01 8.9872700000000000 2008-01-01 11.8096000000000000 2009-01-01 14.7478000000000000 2010-01-01 16.4606000000000000 2011-01-01 18.6330000000000000 2012-01-01 19.8168000000000000 2013-01-01 18.9806000000000000 2014-01-01 18.8262000000000000 2015-01-01 18.1052000000000000 2016-01-01 17.7121000000000000