Year Percent 1973-01-01 16.557000000000002 1974-01-01 14.456900000000000 1975-01-01 13.701900000000000 1976-01-01 13.881700000000000 1977-01-01 14.860400000000000 1978-01-01 18.689100000000000 1979-01-01 20.885500000000000 1980-01-01 18.696300000000000 1981-01-01 15.413500000000000 1982-01-01 14.461400000000000 1983-01-01 14.569500000000000 1984-01-01 14.423300000000000 1985-01-01 14.912400000000000 1986-01-01 15.749900000000000 1987-01-01 14.219700000000000 1988-01-01 13.535500000000000 1989-01-01 20.148700000000000 1990-01-01 20.148700000000000 1991-01-01 43.589900000000000 1992-01-01 81.258200000000000 1993-01-01 134.124000000000000 1994-01-01 192.872000000000000 1995-01-01 182.986000000000000 1996-01-01 83.672200000000000 1997-01-01 26.230300000000000 1998-01-01 216.500000000000000 1999-01-01 313.490000000000000 2000-01-01 191.782000000000000 2001-01-01 217.904000000000020 2002-01-01 286.147999999999970 2003-01-01 396.070999999999970 2004-01-01 356.363000000000060 2005-01-01 388.147000000000000 2006-01-01 435.850000000000000 2007-01-01 476.418000000000000 2008-01-01 603.959000000000100 2009-01-01 840.088000000000100 2010-01-01 14.325500000000000 2011-01-01 15.312999999999999 2012-01-01 16.212100000000000 2013-01-01 18.574300000000000