Year	Percent
1991-01-01	23.1639995574951
1992-01-01	23.2689990997314
1993-01-01	23.2040004730225
1994-01-01	23.1620006561279
1995-01-01	23.1720008850098
1996-01-01	22.3670005798340
1997-01-01	21.4969997406006
1998-01-01	20.6310005187988
1999-01-01	19.5909996032715
2000-01-01	18.8969993591309
2001-01-01	17.8549995422363
2002-01-01	19.2369995117188
2003-01-01	20.9829998016357
2004-01-01	25.2369995117188
2005-01-01	25.9960002899170
2006-01-01	23.1299991607666
2007-01-01	24.2150001525879
2008-01-01	18.8099994659424
2009-01-01	21.6650009155273
2010-01-01	23.0970001220703
2011-01-01	21.9930000305176
2012-01-01	24.2649993896484
2013-01-01	23.5049991607666
2014-01-01	24.4419994354248
2015-01-01	25.9190006256104
2016-01-01	23.5659999847412
2017-01-01	24.4459991455078