Year	Percent
1991-01-01	68.7440032958984
1992-01-01	68.6959991455078
1993-01-01	68.6200027465820
1994-01-01	68.4990005493164
1995-01-01	68.3249969482422
1996-01-01	68.2109985351563
1997-01-01	68.0410003662109
1998-01-01	67.9440002441406
1999-01-01	67.7249984741211
2000-01-01	67.5530014038086
2001-01-01	67.4329986572266
2002-01-01	67.3259963989258
2003-01-01	67.1979980468750
2004-01-01	67.0559997558594
2005-01-01	66.9130020141602
2006-01-01	66.8290023803711
2007-01-01	66.7509994506836
2008-01-01	66.6940002441406
2009-01-01	66.6640014648438
2010-01-01	66.6579971313477
2011-01-01	66.7160034179688
2012-01-01	66.8270034790039
2013-01-01	66.9089965820313
2014-01-01	66.9940032958984
2015-01-01	67.0520019531250
2016-01-01	67.1579971313477
2017-01-01	67.2600021362305