Year	Percent
1968-01-01	0.4064010000000000
1969-01-01	1.0777500000000000
1970-01-01	2.1016300000000000
1971-01-01	3.7139100000000000
1972-01-01	3.7915099999999997
1973-01-01	2.8310900000000000
1974-01-01	3.4013900000000000
1975-01-01	4.4232300000000000
1976-01-01	4.1882400000000000
1977-01-01	3.4405600000000000
1978-01-01	4.3538800000000000
1979-01-01	7.3898899999999990
1980-01-01	9.8513000000000000
1981-01-01	10.0885000000000000
1982-01-01	10.1609000000000000
1983-01-01	9.6786900000000000
1984-01-01	9.8001300000000010
1985-01-01	12.0417000000000000
1986-01-01	13.9590000000000010
1987-01-01	12.0359000000000000
1988-01-01	8.2989300000000000
1989-01-01	7.6874199999999995
1990-01-01	12.6582000000000000
1991-01-01	15.2545000000000000
1992-01-01	14.3805000000000000
1993-01-01	17.3769000000000000
1994-01-01	15.6184000000000000
1995-01-01	12.5083000000000000
1996-01-01	10.4959999999999990
1997-01-01	7.5370100000000000
1998-01-01	4.1467600000000000
1999-01-01	3.1436900000000003
2000-01-01	3.0603400000000000
2001-01-01	2.8815400000000000
2002-01-01	2.4873200000000000
2003-01-01	1.9912599999999998
2004-01-01	1.9549500000000000
2005-01-01	2.4963800000000000
2006-01-01	2.8244000000000000
2007-01-01	2.6618800000000000
2008-01-01	2.2076200000000000
2009-01-01	2.6027400000000003
2010-01-01	2.7646100000000000
2011-01-01	2.4081400000000000
2012-01-01	2.5657700000000000
2013-01-01	2.7705900000000003
2014-01-01	2.8692000000000000
2015-01-01	3.0760000000000000
2016-01-01	3.0181200000000000