Year Percent 1960-01-01 11.574400000000000 1961-01-01 10.972500000000000 1962-01-01 11.289100000000000 1963-01-01 11.553600000000000 1964-01-01 12.687999999999999 1965-01-01 14.277100000000000 1966-01-01 16.074500000000000 1967-01-01 17.738600000000000 1968-01-01 20.171800000000000 1969-01-01 22.355700000000000 1970-01-01 24.016400000000000 1971-01-01 28.807600000000000 1972-01-01 35.922200000000000 1973-01-01 40.571300000000000 1974-01-01 48.400500000000000 1975-01-01 51.980000000000000 1976-01-01 52.245400000000000 1977-01-01 51.535400000000000 1978-01-01 46.397400000000000 1979-01-01 46.610100000000000 1980-01-01 45.174500000000000 1981-01-01 47.063200000000000 1982-01-01 46.797800000000000 1983-01-01 45.482100000000000 1984-01-01 44.073200000000000 1985-01-01 43.078999999999990 1986-01-01 43.342700000000000 1987-01-01 45.187600000000000 1988-01-01 47.465400000000000 1989-01-01 41.799600000000000 1990-01-01 39.042900000000000 1991-01-01 40.562800000000000 1992-01-01 44.588900000000000 1993-01-01 50.561400000000000 1994-01-01 57.589400000000000 1995-01-01 65.355200000000000 1996-01-01 61.436400000000000 1997-01-01 63.819400000000000 1998-01-01 70.420800000000000 1999-01-01 80.341600000000000 2000-01-01 87.984900000000000 2001-01-01 91.912800000000000 2002-01-01 84.643900000000000 2003-01-01 73.330300000000000 2004-01-01 68.901600000000000 2005-01-01 70.806400000000000 2006-01-01 72.593800000000000 2007-01-01 72.737200000000000 2008-01-01 74.375100000000000 2009-01-01 73.162800000000000 2010-01-01 72.724700000000000 2011-01-01 70.603000000000010 2012-01-01 70.445800000000000 2013-01-01 64.215400000000000 2014-01-01 66.602300000000000 2015-01-01 76.895300000000000 2016-01-01 79.846900000000000