Year	Percent
1991-01-01	17.3565110888034
1992-01-01	17.3611106240812
1993-01-01	18.9975091949996
1994-01-01	20.1612060474673
1995-01-01	20.3864825317519
1996-01-01	20.7695367977258
1997-01-01	21.0338248247068
1998-01-01	21.0653443053969
1999-01-01	21.3193117579641
2000-01-01	19.4133479805971
2001-01-01	18.5432758599541
2002-01-01	19.1584651694174
2003-01-01	19.3382710987193
2004-01-01	19.1739966329667
2005-01-01	18.6123479653393
2006-01-01	17.4676580045622
2007-01-01	16.0449726926013
2008-01-01	15.9859174721724
2009-01-01	19.7983394221666
2010-01-01	19.9066737701937
2011-01-01	19.7460184854969
2012-01-01	20.4242841954610
2013-01-01	20.9090972038756
2014-01-01	20.6854845264730
2015-01-01	20.1215997729302
2016-01-01	19.2865267973533
2017-01-01	18.2768107681631