Year	Percent
1991-01-01	69.6370010375977
1992-01-01	69.1250000000000
1993-01-01	69.1340026855469
1994-01-01	68.8479995727539
1995-01-01	68.6460037231445
1996-01-01	68.8659973144531
1997-01-01	69.2419967651367
1998-01-01	69.4260025024414
1999-01-01	69.7379989624023
2000-01-01	70.8069992065430
2001-01-01	71.4290008544922
2002-01-01	71.7409973144531
2003-01-01	71.5550003051758
2004-01-01	71.4629974365234
2005-01-01	71.3199996948242
2006-01-01	71.1839981079102
2007-01-01	70.9700012207031
2008-01-01	70.7630004882813
2009-01-01	71.1589965820313
2010-01-01	70.9100036621094
2011-01-01	70.3889999389648
2012-01-01	70.2710037231445
2013-01-01	70.2040023803711
2014-01-01	70.2040023803711
2015-01-01	70.1009979248047
2016-01-01	70.0449981689453
2017-01-01	70.0019989013672