Year	Percent
1976-01-01	3.0868300000000000
1977-01-01	5.7654600000000000
1978-01-01	7.3473000000000000
1979-01-01	7.6193300000000010
1980-01-01	8.6435100000000010
1981-01-01	7.3561000000000000
1982-01-01	8.4232400000000000
1983-01-01	10.2476000000000000
1984-01-01	8.2846100000000000
1985-01-01	8.1460900000000000
1986-01-01	7.6691500000000000
1987-01-01	6.5380199999999995
1988-01-01	4.8656700000000000
1989-01-01	5.0217900000000000
1990-01-01	5.0143600000000000
1991-01-01	3.4073300000000004
1992-01-01	3.2355600000000000
1993-01-01	2.8094900000000003
1994-01-01	3.3708199999999997
1995-01-01	2.8237700000000000
1996-01-01	2.0278700000000000
1997-01-01	2.7345700000000000
1998-01-01	1.8844900000000002
1999-01-01	1.5816100000000000
2000-01-01	1.4536400000000000
2001-01-01	2.0204700000000000
2002-01-01	4.9151700000000000
2003-01-01	4.7618599999999995
2004-01-01	4.0264200000000000
2005-01-01	3.9086000000000000
2006-01-01	3.7307699999999997
2007-01-01	3.9360600000000000
2008-01-01	4.1386900000000000
2009-01-01	5.1839800000000000
2010-01-01	5.4620200000000000
2011-01-01	5.7414400000000000
2012-01-01	6.2424300000000010
2013-01-01	6.3269100000000000
2014-01-01	7.0567800000000010
2015-01-01	7.1356699999999990
2016-01-01	7.1084399999999990
2017-01-01	6.4564300000000000