Year	Percent
1991-01-01	63.0890007019043
1992-01-01	62.8950004577637
1993-01-01	63.1170005798340
1994-01-01	63.3310012817383
1995-01-01	63.9350013732910
1996-01-01	63.8129997253418
1997-01-01	63.7270011901855
1998-01-01	63.6380004882813
1999-01-01	63.2910003662109
2000-01-01	62.9469985961914
2001-01-01	62.5919990539551
2002-01-01	62.2239990234375
2003-01-01	61.8370018005371
2004-01-01	61.4290008544922
2005-01-01	61.0040016174316
2006-01-01	60.5789985656738
2007-01-01	60.1419982910156
2008-01-01	59.6899986267090
2009-01-01	59.2220001220703
2010-01-01	58.7420005798340
2011-01-01	58.2540016174316
2012-01-01	57.7579994201660
2013-01-01	57.2690010070801
2014-01-01	56.7929992675781
2015-01-01	56.3380012512207
2016-01-01	55.8769989013672
2017-01-01	55.8250007629395