Year Percent 1960-01-01 97.677100000000000 1961-01-01 97.123300000000000 1962-01-01 96.157900000000000 1963-01-01 95.058300000000000 1964-01-01 92.835500000000000 1965-01-01 91.452600000000000 1966-01-01 89.302800000000000 1967-01-01 85.421500000000000 1968-01-01 82.370700000000000 1969-01-01 81.982700000000000 1970-01-01 83.247300000000000 1971-01-01 85.103100000000000 1972-01-01 85.901500000000000 1973-01-01 86.728400000000000 1974-01-01 88.155100000000000 1975-01-01 87.644300000000000 1976-01-01 85.691000000000000 1977-01-01 83.241800000000000 1978-01-01 76.670300000000000 1979-01-01 72.047800000000000 1980-01-01 70.883400000000000 1981-01-01 62.838300000000000 1982-01-01 56.415800000000000 1983-01-01 56.232400000000000 1984-01-01 52.847400000000000 1985-01-01 54.457700000000000 1986-01-01 53.335700000000000 1987-01-01 53.261200000000000 1988-01-01 55.966700000000000 1989-01-01 57.964700000000000 1990-01-01 60.092400000000000 1991-01-01 60.137700000000000 1992-01-01 63.086600000000000 1993-01-01 69.406600000000000 1994-01-01 72.825400000000000 1995-01-01 70.803500000000000 1996-01-01 61.266999999999996 1997-01-01 59.728400000000000 1998-01-01 63.972900000000000 1999-01-01 71.641600000000000 2000-01-01 81.247900000000000 2001-01-01 89.707500000000000 2002-01-01 94.796600000000000 2003-01-01 95.659400000000000 2004-01-01 96.285900000000000 2005-01-01 96.719900000000000 2006-01-01 97.169100000000000 2007-01-01 97.946800000000000 2008-01-01 98.635000000000000 2009-01-01 98.975100000000000 2010-01-01 99.161100000000000 2011-01-01 99.342600000000000 2012-01-01 99.521100000000000 2013-01-01 99.677000000000000 2014-01-01 99.815600000000000 2015-01-01 99.942600000000000 2016-01-01 100.000000000000000