Year Percent 1970-01-01 111.643999999999990 1971-01-01 90.100500000000000 1972-01-01 79.290800000000000 1973-01-01 68.110800000000000 1974-01-01 53.350800000000000 1975-01-01 55.373000000000005 1976-01-01 45.403999999999996 1977-01-01 41.066100000000000 1978-01-01 36.271400000000000 1979-01-01 35.302800000000000 1980-01-01 32.087300000000000 1981-01-01 32.828900000000000 1982-01-01 31.243800000000000 1983-01-01 29.837400000000000 1984-01-01 29.824500000000000 1985-01-01 30.991400000000000 1986-01-01 34.553100000000000 1987-01-01 35.772900000000000 1988-01-01 38.810200000000000 1989-01-01 40.091200000000000 1990-01-01 41.485800000000000 1991-01-01 41.096200000000000 1992-01-01 42.374600000000000 1993-01-01 48.612800000000000 1994-01-01 54.919500000000000 1995-01-01 58.953100000000000 1996-01-01 60.757000000000000 1997-01-01 62.362100000000000 1998-01-01 61.261000000000000 1999-01-01 64.128200000000000 2000-01-01 67.928600000000000 2001-01-01 76.947900000000000 2002-01-01 82.654900000000000 2003-01-01 81.870100000000000 2004-01-01 91.537700000000000 2005-01-01 82.691900000000000 2006-01-01 80.529000000000000 2007-01-01 79.284800000000000 2008-01-01 80.787900000000000 2009-01-01 88.970600000000000 2010-01-01 94.441800000000000 2011-01-01 94.442600000000000 2012-01-01 89.169900000000000 2013-01-01 83.567300000000000 2014-01-01 81.066400000000000 2015-01-01 78.513300000000000 2016-01-01 79.010400000000000