Year Percent 1960-01-01 47.33950000000000 1961-01-01 51.66410000000000 1962-01-01 56.59980000000000 1963-01-01 58.72580000000000 1964-01-01 42.34590000000000 1965-01-01 32.14420000000000 1966-01-01 33.79260000000000 1967-01-01 37.28740000000000 1968-01-01 38.38610000000000 1969-01-01 40.40050000000000 1970-01-01 40.70220000000000 1971-01-01 46.79570000000000 1972-01-01 51.69150000000000 1973-01-01 57.19870000000000 1974-01-01 63.96630000000000 1975-01-01 85.01850000000000 1976-01-01 85.13930000000000 1977-01-01 93.08440000000000 1978-01-01 98.53890000000000 1979-01-01 105.06500000000000 1980-01-01 109.62600000000000 1981-01-01 120.28000000000000 1982-01-01 121.30799999999999 1983-01-01 121.71300000000000 1984-01-01 122.28800000000000 1985-01-01 139.03200000000000 1986-01-01 153.96600000000000 1987-01-01 183.16700000000000 1988-01-01 220.98400000000000 1989-01-01 238.79900000000000 1990-01-01 249.20500000000000 1991-01-01 238.08300000000000 1992-01-01 255.34400000000002 1993-01-01 255.34400000000002 1994-01-01 282.79600000000000 1995-01-01 275.60100000000000 1996-01-01 279.04600000000000 1997-01-01 300.99300000000000 1998-01-01 300.99300000000000 1999-01-01 300.99300000000000 2000-01-01 289.54100000000000 2001-01-01 338.44199999999995 2002-01-01 330.81699999999995 2003-01-01 335.67400000000004 2004-01-01 342.06400000000000 2005-01-01 369.23199999999997 2006-01-01 393.29100000000000 2007-01-01 422.09300000000000 2008-01-01 472.04900000000004 2009-01-01 434.35900000000004 2010-01-01 342.80000000000000 2011-01-01 333.76500000000000 2012-01-01 330.28500000000000 2013-01-01 327.16700000000003 2014-01-01 348.16200000000000 2015-01-01 380.38800000000003 2016-01-01 399.88699999999994