Year	Percent
1991-01-01	27.3939990997314
1992-01-01	28.4610004425049
1993-01-01	28.1270008087158
1994-01-01	28.7089996337891
1995-01-01	28.9169998168945
1996-01-01	28.9519996643066
1997-01-01	28.8190002441406
1998-01-01	28.4939994812012
1999-01-01	28.6459999084473
2000-01-01	28.1800003051758
2001-01-01	27.9599990844727
2002-01-01	28.0489997863770
2003-01-01	27.8680000305176
2004-01-01	27.7980003356934
2005-01-01	27.6140003204346
2006-01-01	27.4260005950928
2007-01-01	27.3530006408691
2008-01-01	27.3479995727539
2009-01-01	27.5909996032715
2010-01-01	27.1079998016357
2011-01-01	27.6119995117188
2012-01-01	27.7070007324219
2013-01-01	27.3229999542236
2014-01-01	27.2569999694824
2015-01-01	27.2870006561279
2016-01-01	27.2670001983643
2017-01-01	27.2759990692139