Year	Percent
1980-01-01	2.000000000000000
1981-01-01	2.000000000000000
1982-01-01	2.500000000000000
1983-01-01	3.000000000000000
1984-01-01	3.000000000000000
1985-01-01	3.000000000000000
1986-01-01	3.000000000000000
1987-01-01	3.000000000000000
1988-01-01	3.000000000000000
1989-01-01	3.000000000000000
1990-01-01	5.058330000000001
1991-01-01	9.675000000000000
1992-01-01	9.050000000000000
1993-01-01	12.100000000000000
1994-01-01	13.241700000000000
1995-01-01	13.291700000000000
1996-01-01	15.066700000000000
1997-01-01	11.220000000000000
1998-01-01	11.860000000000000
1999-01-01	10.370000000000000
2000-01-01	10.070000000000000
2001-01-01	10.180000000000000
2002-01-01	9.910000000000000
2003-01-01	9.910000000000000
2004-01-01	9.210000000000000
2005-01-01	8.290000000000000
2006-01-01	8.220000000000000
2007-01-01	8.120000000000000
2008-01-01	8.450000000000000
2009-01-01	8.010000000000000
2010-01-01	7.940000000000000
2011-01-01	8.330000000000000
2012-01-01	8.100000000000000
2013-01-01	8.240000000000000
2014-01-01	8.180000000000000
2015-01-01	7.640000000000000
2016-01-01	7.590000000000000