Year Percent 1963-01-01 97.8561 1964-01-01 94.2447 1965-01-01 91.0923 1966-01-01 90.6585 1967-01-01 90.7563 1968-01-01 88.7231 1969-01-01 89.1320 1970-01-01 91.1058 1971-01-01 95.8863 1972-01-01 95.8863 1973-01-01 95.8863 1974-01-01 99.0700 1975-01-01 96.7532 1976-01-01 94.1268 1977-01-01 89.4198 1978-01-01 85.2929 1979-01-01 83.1837 1980-01-01 84.6850 1981-01-01 92.7382 1982-01-01 97.9953 1983-01-01 98.8206 1984-01-01 99.8673 1985-01-01 99.8673 1986-01-01 96.7612 1987-01-01 87.8015 1988-01-01 80.1535 1989-01-01 77.2392 1990-01-01 82.4875 1991-01-01 88.9638 1992-01-01 85.8642 1993-01-01 81.8521 1994-01-01 79.6136 1995-01-01 78.1421 1996-01-01 76.2729 1997-01-01 79.0375 1998-01-01 74.7778 1999-01-01 68.3749 2000-01-01 70.8272 2001-01-01 69.1637 2002-01-01 67.9975 2003-01-01 70.5897 2004-01-01 70.3227 2005-01-01 71.1666 2006-01-01 79.8236 2007-01-01 87.6682 2008-01-01 93.0185 2009-01-01 93.3232 2010-01-01 80.3696 2011-01-01 78.4923 2012-01-01 82.8841 2013-01-01 85.6731 2014-01-01 87.0179 2015-01-01 83.0194 2016-01-01 79.7376