Year	Percent
1991-01-01	28.5440006256104
1992-01-01	26.5219993591309
1993-01-01	26.4659996032715
1994-01-01	32.5620002746582
1995-01-01	38.3899993896484
1996-01-01	30.5049991607666
1997-01-01	28.5230007171631
1998-01-01	33.6520004272461
1999-01-01	20.9850006103516
2000-01-01	20.5569992065430
2001-01-01	19.0189990997314
2002-01-01	17.7409992218018
2003-01-01	17.2019996643066
2004-01-01	15.6110000610352
2005-01-01	15.8470001220703
2006-01-01	16.7539997100830
2007-01-01	16.3740005493164
2008-01-01	18.5289993286133
2009-01-01	17.6009998321533
2010-01-01	17.5939998626709
2011-01-01	17.9740009307861
2012-01-01	18.6639995574951
2013-01-01	19.0520000457764
2014-01-01	19.9360008239746
2015-01-01	20.6989994049072
2016-01-01	18.6219997406006
2017-01-01	17.9580001831055