Year	Percent
1980-01-01	15.96083333333330
1981-01-01	15.81166666666670
1982-01-01	15.98750000000000
1983-01-01	16.90916666666670
1984-01-01	16.52250000000000
1985-01-01	13.36750000000000
1986-01-01	11.35416666666670
1987-01-01	12.81333333333330
1988-01-01	11.74416666666670
1989-01-01	13.60058333333330
1990-01-01	14.67750000000000
1991-01-01	12.36055098000000
1992-01-01	11.69519017333330
1993-01-01	10.21079471050000
1994-01-01	9.99779112466666
1995-01-01	11.27093513683330
1996-01-01	8.73646118525000
1997-01-01	6.40153466491667
1998-01-01	4.83292649833333
1999-01-01	4.72731143825000
2000-01-01	5.52586605983333
2001-01-01	5.11528379691667
2002-01-01	4.95764101216667
2003-01-01	4.12304358466667
2004-01-01	4.10414294483333
2005-01-01	3.38634953491667
2006-01-01	3.78431006525000
2007-01-01	4.30662664041667
2008-01-01	4.36373224600000
2009-01-01	3.97429824425000
2010-01-01	4.25000089883333
2011-01-01	5.43689422550000
2012-01-01	5.84653721733333
2013-01-01	4.56196203883333
2014-01-01	2.72183108208333
2015-01-01	1.73508728008333
2016-01-01	1.39330222033333
2017-01-01	1.55786583083333