Year Percent 1960-01-01 38.88550000000000 1961-01-01 37.09090000000000 1962-01-01 35.45470000000000 1963-01-01 37.01610000000000 1964-01-01 41.96660000000000 1965-01-01 34.91650000000000 1966-01-01 36.22410000000000 1967-01-01 35.60270000000000 1968-01-01 41.38390000000000 1969-01-01 41.61400000000000 1970-01-01 43.14450000000000 1971-01-01 41.19770000000000 1972-01-01 42.49660000000000 1973-01-01 47.37890000000000 1974-01-01 63.03310000000000 1975-01-01 79.15910000000000 1976-01-01 65.52510000000000 1977-01-01 61.42850000000000 1978-01-01 62.05090000000000 1979-01-01 59.54350000000000 1980-01-01 58.49630000000000 1981-01-01 57.01850000000000 1982-01-01 55.38180000000000 1983-01-01 56.95960000000000 1984-01-01 54.06510000000000 1985-01-01 55.65290000000000 1986-01-01 57.56210000000000 1987-01-01 57.88210000000000 1988-01-01 71.73890000000000 1989-01-01 86.63400000000000 1990-01-01 91.20950000000000 1991-01-01 101.14200000000001 1992-01-01 102.03600000000000 1993-01-01 111.24900000000000 1994-01-01 113.26500000000000 1995-01-01 104.79899999999999 1996-01-01 116.55000000000000 1997-01-01 125.04100000000000 1998-01-01 128.45000000000000 1999-01-01 136.08500000000000 2000-01-01 143.41700000000000 2001-01-01 145.63900000000000 2002-01-01 83.51670000000000 2003-01-01 83.83300000000000 2004-01-01 82.48330000000000 2005-01-01 116.72900000000000 2006-01-01 152.84700000000000 2007-01-01 162.69200000000000 2008-01-01 211.14200000000000 2009-01-01 218.60900000000000 2010-01-01 226.12200000000000 2011-01-01 237.16299999999998 2012-01-01 247.86900000000003 2013-01-01 260.70400000000000 2014-01-01 257.28200000000000 2015-01-01 247.98200000000000