Year Percent 1960-01-01 12.141600000000000 1961-01-01 13.677900000000000 1962-01-01 14.062900000000000 1963-01-01 13.862600000000000 1964-01-01 13.142100000000000 1965-01-01 12.469300000000000 1966-01-01 12.733300000000000 1967-01-01 12.473600000000000 1968-01-01 12.724900000000000 1969-01-01 11.900300000000000 1970-01-01 9.386690000000000 1971-01-01 9.261090000000000 1972-01-01 10.056200000000000 1973-01-01 10.745800000000000 1974-01-01 10.678600000000000 1975-01-01 12.015600000000000 1976-01-01 12.554500000000000 1977-01-01 12.949600000000000 1978-01-01 13.243400000000000 1979-01-01 12.786000000000000 1980-01-01 12.011000000000000 1981-01-01 13.157000000000000 1982-01-01 13.699600000000000 1983-01-01 14.822000000000001 1984-01-01 15.338100000000000 1985-01-01 14.599000000000000 1986-01-01 14.599000000000000 1987-01-01 14.599000000000000 1988-01-01 14.599000000000000 1989-01-01 14.599000000000000 1990-01-01 13.335200000000000 1991-01-01 14.812999999999999 1992-01-01 18.505500000000000 1993-01-01 20.537600000000000 1994-01-01 20.456800000000000 1995-01-01 23.316999999999997 1996-01-01 23.170700000000000 1997-01-01 32.227100000000000 1998-01-01 39.872200000000000 1999-01-01 42.833300000000000 2000-01-01 46.470700000000000 2001-01-01 45.298200000000000 2002-01-01 45.600700000000000 2003-01-01 44.810000000000000 2004-01-01 45.553400000000000 2005-01-01 47.860400000000000 2006-01-01 50.681400000000000 2007-01-01 57.943400000000000 2008-01-01 66.066600000000000 2009-01-01 72.911600000000000 2010-01-01 70.287800000000000 2011-01-01 67.273000000000000 2012-01-01 69.661500000000000 2013-01-01 67.983400000000000 2014-01-01 66.914700000000000 2015-01-01 63.874800000000000 2016-01-01 63.171000000000010