Year Percent 1960-01-01 10.9405000000000000 1961-01-01 11.2020000000000000 1962-01-01 11.6757000000000000 1963-01-01 12.0100000000000000 1964-01-01 12.5197000000000000 1965-01-01 11.6633000000000000 1966-01-01 11.5273000000000000 1967-01-01 11.9065000000000000 1968-01-01 12.8216000000000000 1969-01-01 13.4709000000000000 1970-01-01 10.2344000000000000 1971-01-01 9.3401600000000010 1972-01-01 10.2479000000000000 1973-01-01 11.5008000000000000 1974-01-01 11.7842000000000000 1975-01-01 10.7858000000000000 1976-01-01 10.9679000000000000 1977-01-01 12.1676000000000000 1978-01-01 13.4885000000000000 1979-01-01 12.1917000000000000 1980-01-01 13.3072000000000000 1981-01-01 12.5007000000000000 1982-01-01 13.5311000000000000 1983-01-01 14.4625000000000000 1984-01-01 12.1818000000000000 1985-01-01 10.7458000000000000 1986-01-01 8.2674300000000010 1987-01-01 7.7374399999999990 1988-01-01 7.8864800000000010 1989-01-01 7.8153000000000000 1990-01-01 9.7713100000000000 1991-01-01 7.3199700000000000 1992-01-01 7.3882900000000000 1993-01-01 7.2906300000000000 1994-01-01 6.8204899999999995 1995-01-01 6.3503300000000005 1996-01-01 6.0240800000000005 1997-01-01 8.7329700000000000 1998-01-01 8.7189400000000000 1999-01-01 9.5056800000000000 2000-01-01 10.6053000000000000 2001-01-01 11.7365000000000000 2002-01-01 12.6881000000000000 2003-01-01 12.8446000000000000 2004-01-01 12.9131000000000000 2005-01-01 15.1826000000000000 2006-01-01 14.2977000000000000 2007-01-01 15.2534000000000000 2008-01-01 16.3851000000000000 2009-01-01 18.2911000000000000 2010-01-01 19.2671000000000000 2011-01-01 19.5079000000000000 2012-01-01 18.5376000000000000 2013-01-01 16.7467000000000000 2014-01-01 18.4939000000000000 2015-01-01 22.8463000000000000 2016-01-01 23.3222000000000000