Year Percent 1967-01-01 91.57130000000000 1968-01-01 85.31640000000000 1969-01-01 88.40600000000000 1970-01-01 95.29290000000000 1971-01-01 97.30780000000000 1972-01-01 93.30450000000000 1973-01-01 94.19690000000000 1974-01-01 98.28220000000000 1975-01-01 98.41570000000000 1976-01-01 88.71030000000000 1977-01-01 76.22570000000000 1978-01-01 70.86820000000000 1979-01-01 68.79850000000000 1980-01-01 68.72760000000000 1981-01-01 64.97840000000000 1982-01-01 60.59900000000000 1983-01-01 59.41530000000000 1984-01-01 59.82710000000000 1985-01-01 63.35960000000000 1986-01-01 71.71640000000000 1987-01-01 85.78880000000000 1988-01-01 96.71190000000000 1989-01-01 99.99810000000000 1990-01-01 99.99790000000000 1991-01-01 93.44130000000000 1992-01-01 91.73140000000000 1993-01-01 96.72010000000000 1994-01-01 96.87799999999999 1995-01-01 97.75860000000000 1996-01-01 98.84590000000000 1997-01-01 98.12070000000000 1998-01-01 95.63310000000000 1999-01-01 95.54020000000000 2000-01-01 97.43200000000000 2001-01-01 97.68720000000000 2002-01-01 98.18410000000000 2003-01-01 99.04180000000000 2004-01-01 99.15000000000000 2005-01-01 98.44460000000000 2006-01-01 97.34540000000000 2007-01-01 98.02890000000000 2008-01-01 99.41090000000000 2009-01-01 99.61870000000000 2010-01-01 99.04720000000000 2011-01-01 97.87140000000000 2012-01-01 98.10740000000000 2013-01-01 98.61030000000000 2014-01-01 98.79740000000000 2015-01-01 99.23620000000000 2016-01-01 99.61410000000000