Year	Percent
1991-01-01	50.5176122957863
1992-01-01	49.6711097064407
1993-01-01	48.5478143950591
1994-01-01	47.9832592280492
1995-01-01	48.0337124770089
1996-01-01	48.0095947810682
1997-01-01	48.1174844387334
1998-01-01	48.5615943180453
1999-01-01	49.2554705306228
2000-01-01	49.9364599199182
2001-01-01	50.3724679689303
2002-01-01	50.5773268153490
2003-01-01	50.7415621286776
2004-01-01	50.7037479380611
2005-01-01	51.2077378161641
2006-01-01	51.8174597609351
2007-01-01	52.5194667394841
2008-01-01	52.6951889337334
2009-01-01	51.4686989239105
2010-01-01	51.0514961225154
2011-01-01	50.9647624164093
2012-01-01	50.4730386625462
2013-01-01	50.0266405286202
2014-01-01	50.1002474603853
2015-01-01	50.4537761376361
2016-01-01	50.9924274676300
2017-01-01	51.3852093175049