Year	Percent
1960-01-01	1.98
1961-01-01	2.33
1962-01-01	2.93
1963-01-01	3.38
1964-01-01	3.85
1965-01-01	4.32
1966-01-01	5.40
1967-01-01	4.51
1968-01-01	6.02
1969-01-01	8.97
1970-01-01	4.90
1971-01-01	4.14
1972-01-01	5.33
1973-01-01	9.95
1974-01-01	8.53
1975-01-01	5.20
1976-01-01	4.65
1977-01-01	6.56
1978-01-01	10.03
1979-01-01	13.78
1980-01-01	18.90
1981-01-01	12.37
1982-01-01	8.95
1983-01-01	9.47
1984-01-01	8.38
1985-01-01	8.27
1986-01-01	6.91
1987-01-01	6.77
1988-01-01	8.76
1989-01-01	8.45
1990-01-01	7.31
1991-01-01	4.43
1992-01-01	2.92
1993-01-01	2.96
1994-01-01	5.45
1995-01-01	5.60
1996-01-01	5.29
1997-01-01	5.50
1998-01-01	4.68
1999-01-01	5.30
2000-01-01	6.40
2001-01-01	1.82
2002-01-01	1.24
2003-01-01	0.98
2004-01-01	2.16
2005-01-01	4.16
2006-01-01	5.24
2007-01-01	4.24
2008-01-01	0.16
2009-01-01	0.12
2010-01-01	0.18
2011-01-01	0.07
2012-01-01	0.16
2013-01-01	0.09
2014-01-01	0.12
2015-01-01	0.24
2016-01-01	0.54
2017-01-01	1.30