Year	Percent
1991-01-01	57.8709983825684
1992-01-01	57.7659988403320
1993-01-01	57.7859992980957
1994-01-01	57.7330017089844
1995-01-01	57.6180000305176
1996-01-01	56.8940010070801
1997-01-01	55.7929992675781
1998-01-01	55.4290008544922
1999-01-01	55.2070007324219
2000-01-01	55.1990013122559
2001-01-01	54.5040016174316
2002-01-01	54.3580017089844
2003-01-01	54.4539985656738
2004-01-01	54.4020004272461
2005-01-01	54.6819992065430
2006-01-01	54.5559997558594
2007-01-01	54.4440002441406
2008-01-01	54.4700012207031
2009-01-01	54.8950004577637
2010-01-01	55.5629997253418
2011-01-01	55.3759994506836
2012-01-01	55.2270011901855
2013-01-01	55.4589996337891
2014-01-01	55.7760009765625
2015-01-01	56.3199996948242
2016-01-01	55.8120002746582
2017-01-01	55.1380004882813