Year Percent 1960-01-01 79.19320000000000 1961-01-01 73.61770000000000 1962-01-01 68.80530000000000 1963-01-01 69.70180000000000 1964-01-01 70.15790000000000 1965-01-01 71.56850000000000 1966-01-01 73.01290000000000 1967-01-01 74.16890000000000 1968-01-01 75.78930000000000 1969-01-01 77.44730000000000 1970-01-01 79.66040000000000 1971-01-01 79.35980000000000 1972-01-01 78.89380000000000 1973-01-01 81.66830000000000 1974-01-01 82.82840000000000 1975-01-01 80.72790000000000 1976-01-01 78.70850000000000 1977-01-01 74.59460000000000 1978-01-01 69.72040000000000 1979-01-01 65.98120000000000 1980-01-01 61.09990000000000 1981-01-01 60.65160000000000 1982-01-01 64.08520000000000 1983-01-01 67.28520000000000 1984-01-01 62.89920000000000 1985-01-01 59.06580000000000 1986-01-01 68.65340000000000 1987-01-01 80.11390000000000 1988-01-01 84.47440000000000 1989-01-01 88.48140000000000 1990-01-01 92.64150000000000 1991-01-01 92.20770000000000 1992-01-01 87.49760000000000 1993-01-01 83.99540000000000 1994-01-01 81.98899999999999 1995-01-01 80.07510000000000 1996-01-01 83.30180000000000 1997-01-01 89.14110000000000 1998-01-01 94.12490000000000 1999-01-01 97.08050000000000 2000-01-01 97.81060000000000 2001-01-01 85.11230000000000 2002-01-01 78.32550000000000 2003-01-01 84.40840000000000 2004-01-01 88.54960000000000 2005-01-01 92.40470000000000 2006-01-01 94.49460000000000 2007-01-01 95.59140000000000 2008-01-01 96.79600000000000 2009-01-01 97.84490000000000 2010-01-01 98.47490000000000 2011-01-01 98.76299999999999 2012-01-01 98.89170000000000 2013-01-01 99.00810000000000 2014-01-01 99.12720000000000 2015-01-01 99.23880000000000 2016-01-01 99.20170000000000