Year Percent 1960-01-01 68.02650000000000 1961-01-01 64.63300000000000 1962-01-01 58.30140000000000 1963-01-01 58.65630000000000 1964-01-01 57.88320000000000 1965-01-01 58.07370000000000 1966-01-01 63.80880000000000 1967-01-01 65.65980000000000 1968-01-01 66.23210000000000 1969-01-01 67.30480000000000 1970-01-01 64.46960000000000 1971-01-01 65.70980000000000 1972-01-01 70.10950000000000 1973-01-01 76.16240000000000 1974-01-01 83.20880000000000 1975-01-01 85.84700000000001 1976-01-01 89.61480000000000 1977-01-01 89.61480000000000 1978-01-01 89.61480000000000 1979-01-01 89.61480000000000 1980-01-01 89.61480000000000 1981-01-01 89.61480000000000 1982-01-01 89.61480000000000 1983-01-01 89.61480000000000 1984-01-01 89.61480000000000 1985-01-01 89.61480000000000 1986-01-01 89.61480000000000 1987-01-01 89.61480000000000 1988-01-01 89.61480000000000 1989-01-01 89.61480000000000 1990-01-01 89.61480000000000 1991-01-01 89.61480000000000 1992-01-01 89.61480000000000 1993-01-01 89.61480000000000 1994-01-01 89.61480000000000 1995-01-01 89.61480000000000 1996-01-01 89.61480000000000 1997-01-01 89.61480000000000 1998-01-01 89.61480000000000 1999-01-01 89.61480000000000 2000-01-01 89.61480000000000 2001-01-01 89.61480000000000 2002-01-01 89.61480000000000 2003-01-01 89.61480000000000 2004-01-01 22.26820000000000 2005-01-01 31.93720000000000 2006-01-01 43.49880000000000 2007-01-01 47.65980000000000 2008-01-01 57.63130000000000 2009-01-01 66.48110000000000 2010-01-01 75.20470000000000 2011-01-01 83.55740000000000 2012-01-01 89.22420000000000 2013-01-01 91.57420000000000 2014-01-01 93.13390000000000 2015-01-01 88.35360000000000 2016-01-01 76.37850000000000