Year Percent 1973-01-01 56.88160000000000 1974-01-01 56.88160000000000 1975-01-01 56.88160000000000 1976-01-01 172.33200000000000 1977-01-01 96.12820000000000 1978-01-01 110.79000000000000 1979-01-01 112.49900000000000 1980-01-01 115.31900000000000 1981-01-01 129.94299999999998 1982-01-01 247.02599999999998 1983-01-01 247.02599999999998 1984-01-01 247.02599999999998 1985-01-01 247.02599999999998 1986-01-01 247.02599999999998 1987-01-01 247.02599999999998 1988-01-01 59.83140000000000 1989-01-01 91.74590000000000 1990-01-01 93.08260000000000 1991-01-01 66.76170000000000 1992-01-01 58.86390000000000 1993-01-01 67.87890000000000 1994-01-01 80.42980000000000 1995-01-01 91.46320000000000 1996-01-01 105.34200000000001 1997-01-01 110.22100000000000 1998-01-01 124.57900000000000 1999-01-01 151.38500000000000 2000-01-01 169.89700000000002 2001-01-01 171.11500000000000 2002-01-01 164.63299999999998 2003-01-01 156.77200000000002 2004-01-01 144.33200000000000 2005-01-01 149.20200000000000 2006-01-01 154.60900000000000 2007-01-01 157.84100000000000 2008-01-01 149.66899999999998 2009-01-01 139.19000000000000 2010-01-01 145.48100000000000 2011-01-01 153.72700000000000 2012-01-01 151.07900000000000 2013-01-01 160.16800000000000 2014-01-01 171.22200000000000 2015-01-01 169.51700000000000 2016-01-01 168.08900000000003