Year Percent 1960-01-01 69.81130000000000 1961-01-01 71.91310000000000 1962-01-01 76.34380000000000 1963-01-01 77.38920000000000 1964-01-01 75.20170000000000 1965-01-01 78.17930000000000 1966-01-01 78.73670000000000 1967-01-01 76.73630000000000 1968-01-01 75.68310000000000 1969-01-01 76.01780000000000 1970-01-01 78.97520000000000 1971-01-01 81.40820000000000 1972-01-01 84.16660000000000 1973-01-01 86.98480000000000 1974-01-01 88.77520000000000 1975-01-01 90.71550000000000 1976-01-01 93.18100000000000 1977-01-01 94.88490000000000 1978-01-01 94.40540000000000 1979-01-01 93.08780000000000 1980-01-01 85.12360000000000 1981-01-01 79.10230000000000 1982-01-01 80.83460000000000 1983-01-01 71.76740000000000 1984-01-01 70.32750000000000 1985-01-01 82.64290000000000 1986-01-01 89.03840000000000 1987-01-01 79.71840000000000 1988-01-01 75.81990000000000 1989-01-01 93.13000000000000 1990-01-01 97.84550000000000 1991-01-01 97.23420000000000 1992-01-01 97.09730000000000 1993-01-01 98.86440000000000 1994-01-01 97.41440000000000 1995-01-01 96.57710000000000 1996-01-01 97.56690000000000 1997-01-01 98.27060000000000 1998-01-01 98.65320000000000 1999-01-01 98.90510000000000 2000-01-01 99.10930000000000 2001-01-01 99.20480000000000 2002-01-01 99.25690000000000 2003-01-01 99.40299999999999 2004-01-01 99.70710000000000 2005-01-01 99.96140000000000 2006-01-01 100.00000000000000 2007-01-01 100.00000000000000 2008-01-01 100.00000000000000 2009-01-01 100.00000000000000 2010-01-01 100.00000000000000 2011-01-01 100.00000000000000 2012-01-01 99.74220000000000 2013-01-01 99.39560000000000 2014-01-01 99.22260000000000 2015-01-01 99.09060000000000 2016-01-01 99.06090000000000