Year	Percent
1991-01-01	19.3540000915527
1992-01-01	18.2649993896484
1993-01-01	15.0670003890991
1994-01-01	15.8889999389648
1995-01-01	16.5219993591309
1996-01-01	22.1229991912842
1997-01-01	23.0599994659424
1998-01-01	28.5440006256104
1999-01-01	38.2400016784668
2000-01-01	39.2039985656738
2001-01-01	27.8050003051758
2002-01-01	28.7169990539551
2003-01-01	26.7240009307861
2004-01-01	26.4930000305176
2005-01-01	23.8360004425049
2006-01-01	25.2430000305176
2007-01-01	22.0160007476807
2008-01-01	22.5860004425049
2009-01-01	23.5820007324219
2010-01-01	21.8099994659424
2011-01-01	21.1410007476807
2012-01-01	19.4990005493164
2013-01-01	18.0919990539551
2014-01-01	17.9090003967285
2015-01-01	17.5680007934570
2016-01-01	17.1919994354248
2017-01-01	18.0599994659424