Year Percent 1973-01-01 38.79850000000000 1974-01-01 38.46480000000000 1975-01-01 40.77460000000000 1976-01-01 41.16560000000000 1977-01-01 41.97230000000000 1978-01-01 42.10450000000000 1979-01-01 41.26230000000000 1980-01-01 42.30220000000000 1981-01-01 43.66010000000000 1982-01-01 45.81990000000000 1983-01-01 48.88360000000000 1984-01-01 51.25760000000000 1985-01-01 55.21220000000000 1986-01-01 59.03030000000000 1987-01-01 63.51640000000000 1988-01-01 68.68800000000000 1989-01-01 74.37630000000000 1990-01-01 79.95490000000000 1991-01-01 89.98590000000000 1992-01-01 91.28530000000000 1993-01-01 84.51290000000000 1994-01-01 73.08360000000000 1995-01-01 65.34890000000000 1996-01-01 63.42010000000000 1997-01-01 57.36500000000000 1998-01-01 54.27500000000000 1999-01-01 57.21750000000000 2000-01-01 57.28790000000000 2001-01-01 59.35190000000000 2002-01-01 59.71340000000000 2003-01-01 62.35380000000000 2004-01-01 64.77440000000000 2005-01-01 69.32790000000000 2006-01-01 73.78420000000000 2007-01-01 76.12340000000000 2008-01-01 81.72980000000000 2009-01-01 90.42700000000000 2010-01-01 91.18600000000000 2011-01-01 93.35150000000000 2012-01-01 97.39620000000000 2013-01-01 99.00800000000000 2014-01-01 100.82799999999999 2015-01-01 101.66300000000000 2016-01-01 101.83300000000000