Year	Percent
1991-01-01	16.7623812799006
1992-01-01	15.5184211643137
1993-01-01	15.5049503472831
1994-01-01	16.5401231381457
1995-01-01	17.6686770891757
1996-01-01	18.4625038200064
1997-01-01	20.0411676411269
1998-01-01	21.6027876566809
1999-01-01	21.9706432361267
2000-01-01	19.3068002941730
2001-01-01	18.6778892015633
2002-01-01	19.3655396506648
2003-01-01	19.3598565297437
2004-01-01	18.7808421154666
2005-01-01	17.7035301566818
2006-01-01	16.9036734730976
2007-01-01	16.0888197471546
2008-01-01	15.9613511664133
2009-01-01	19.1153901861051
2010-01-01	18.2030078299077
2011-01-01	17.1305473794730
2012-01-01	16.5982024875942
2013-01-01	16.6329636973165
2014-01-01	17.3711746591181
2015-01-01	17.9228421834011
2016-01-01	17.8576329295339
2017-01-01	17.8914953697180