Year Percent 1975-01-01 33.70220000000000 1976-01-01 35.80800000000000 1977-01-01 37.01230000000000 1978-01-01 34.90420000000000 1979-01-01 33.76560000000000 1980-01-01 34.37850000000000 1981-01-01 35.48710000000000 1982-01-01 32.59200000000000 1983-01-01 34.91480000000000 1984-01-01 36.61770000000000 1985-01-01 38.52150000000000 1986-01-01 46.17260000000000 1987-01-01 38.95280000000000 1988-01-01 29.43480000000000 1989-01-01 27.69830000000000 1990-01-01 25.58810000000000 1991-01-01 36.50510000000000 1992-01-01 50.00080000000000 1993-01-01 51.26030000000000 1994-01-01 51.11090000000000 1995-01-01 50.28300000000000 1996-01-01 46.97700000000000 1997-01-01 48.92910000000000 1998-01-01 55.05580000000000 1999-01-01 53.66850000000000 2000-01-01 47.65990000000000 2001-01-01 47.65990000000000 2002-01-01 47.65990000000000 2003-01-01 47.65990000000000 2004-01-01 53.15450000000000 2005-01-01 48.54430000000000 2006-01-01 56.40520000000000 2007-01-01 71.34530000000000 2008-01-01 85.94590000000000 2009-01-01 114.07799999999999 2010-01-01 103.59600000000000 2011-01-01 96.15440000000000 2012-01-01 96.38240000000000 2013-01-01 96.19630000000000 2014-01-01 95.10640000000000 2015-01-01 104.72800000000000