Year Percent 1965-01-01 99.10580000000000 1966-01-01 97.07090000000000 1967-01-01 97.33140000000000 1968-01-01 97.24230000000000 1969-01-01 97.11420000000000 1970-01-01 97.23460000000000 1971-01-01 98.54070000000000 1972-01-01 99.85820000000000 1973-01-01 99.85820000000000 1974-01-01 99.85820000000000 1975-01-01 99.85820000000000 1976-01-01 99.85820000000000 1977-01-01 99.85820000000000 1978-01-01 99.85820000000000 1979-01-01 99.85820000000000 1980-01-01 99.85820000000000 1981-01-01 99.85820000000000 1982-01-01 99.85820000000000 1983-01-01 99.85820000000000 1984-01-01 99.85820000000000 1985-01-01 99.85820000000000 1986-01-01 99.85820000000000 1987-01-01 99.85820000000000 1988-01-01 99.85820000000000 1989-01-01 99.85820000000000 1990-01-01 99.85820000000000 1991-01-01 99.85820000000000 1992-01-01 99.85820000000000 1993-01-01 99.85820000000000 1994-01-01 99.85820000000000 1995-01-01 99.85820000000000 1996-01-01 99.85820000000000 1997-01-01 99.85820000000000 1998-01-01 99.85820000000000 1999-01-01 99.85820000000000 2000-01-01 98.62930000000000 2001-01-01 97.32440000000000 2002-01-01 97.31600000000000 2003-01-01 97.27450000000000 2004-01-01 97.13280000000000 2005-01-01 97.06570000000000 2006-01-01 97.25910000000000 2007-01-01 97.63660000000000 2008-01-01 97.91280000000000 2009-01-01 97.97660000000000 2010-01-01 98.05450000000000 2011-01-01 98.34899999999999 2012-01-01 98.60020000000000 2013-01-01 98.73180000000000 2014-01-01 98.84190000000000 2015-01-01 98.82070000000000 2016-01-01 98.71550000000000