Year Percent 1962-01-01 20.33690000000000 1963-01-01 21.58320000000000 1964-01-01 21.80410000000000 1965-01-01 23.89480000000000 1966-01-01 26.04220000000000 1967-01-01 27.55200000000000 1968-01-01 31.99260000000000 1969-01-01 34.08490000000000 1970-01-01 31.96390000000000 1971-01-01 24.94570000000000 1972-01-01 29.83600000000000 1973-01-01 27.91820000000000 1974-01-01 17.20240000000000 1975-01-01 20.86490000000000 1976-01-01 23.62760000000000 1977-01-01 30.53520000000000 1978-01-01 36.98280000000000 1979-01-01 28.12410000000000 1980-01-01 30.12250000000000 1981-01-01 45.18070000000000 1982-01-01 64.34700000000000 1983-01-01 72.11270000000000 1984-01-01 72.85410000000000 1985-01-01 74.37390000000000 1986-01-01 91.74030000000000 1987-01-01 77.74750000000000 1988-01-01 88.07220000000000 1989-01-01 75.99180000000000 1990-01-01 75.99180000000000 1991-01-01 177.02800000000000 1992-01-01 96.50190000000000 1993-01-01 80.57180000000000 1994-01-01 83.47220000000000 1995-01-01 82.28250000000000 1996-01-01 74.88200000000000 1997-01-01 77.15920000000000 1998-01-01 90.55910000000000 1999-01-01 78.30750000000000 2000-01-01 64.19490000000000 2001-01-01 76.68200000000000 2002-01-01 77.22860000000000 2003-01-01 66.91510000000000 2004-01-01 59.63970000000000 2005-01-01 50.01210000000000 2006-01-01 46.53250000000000 2007-01-01 50.84200000000000 2008-01-01 50.31520000000000 2009-01-01 73.94380000000000 2010-01-01 73.99510000000000 2011-01-01 60.62720000000000 2012-01-01 56.39000000000000 2013-01-01 60.14530000000000 2014-01-01 68.61399999999999 2015-01-01 94.94700000000000 2016-01-01 100.07000000000000