Year	Percent
1991-01-01	71.3759994506836
1992-01-01	71.3889999389648
1993-01-01	71.5419998168945
1994-01-01	71.6630020141602
1995-01-01	71.7570037841797
1996-01-01	71.7969970703125
1997-01-01	71.8030014038086
1998-01-01	71.7750015258789
1999-01-01	71.7149963378906
2000-01-01	71.6230010986328
2001-01-01	71.4990005493164
2002-01-01	71.3239974975586
2003-01-01	71.3389968872070
2004-01-01	71.3050003051758
2005-01-01	71.2279968261719
2006-01-01	71.0930023193359
2007-01-01	70.9189987182617
2008-01-01	70.7139968872070
2009-01-01	70.4879989624023
2010-01-01	70.3059997558594
2011-01-01	68.9860000610352
2012-01-01	68.9789962768555
2013-01-01	68.9599990844727
2014-01-01	68.9390029907227
2015-01-01	68.9280014038086
2016-01-01	68.9889984130859
2017-01-01	69.1360015869141