Year	Percent
1970-01-01	8.1949100000000000
1971-01-01	9.3178700000000000
1972-01-01	8.8983800000000000
1973-01-01	7.3297300000000005
1974-01-01	7.6642899999999990
1975-01-01	9.0695400000000000
1976-01-01	9.8856000000000000
1977-01-01	8.7819300000000010
1978-01-01	8.8107300000000000
1979-01-01	10.2949000000000000
1980-01-01	10.3344000000000000
1981-01-01	11.4657000000000000
1982-01-01	11.3267000000000000
1983-01-01	10.7323000000000000
1984-01-01	9.9671500000000000
1985-01-01	9.6478700000000000
1986-01-01	8.7933100000000000
1987-01-01	8.5354800000000000
1988-01-01	10.2295000000000000
1989-01-01	10.7976000000000000
1990-01-01	12.8392000000000000
1991-01-01	15.8135000000000000
1992-01-01	16.1465000000000000
1993-01-01	14.7563000000000000
1994-01-01	14.4993000000000000
1995-01-01	13.0615000000000000
1996-01-01	11.8316000000000000
1997-01-01	11.3435000000000000
1998-01-01	11.2205000000000000
1999-01-01	10.8325000000000000
2000-01-01	10.7035000000000000
2001-01-01	9.1198700000000000
2002-01-01	8.8073000000000000
2003-01-01	10.7659000000000000
2004-01-01	13.2619000000000000
2005-01-01	15.0623000000000000
2006-01-01	16.8848000000000000
2007-01-01	18.9420000000000000
2008-01-01	19.6378000000000000
2009-01-01	19.1976000000000000
2010-01-01	18.9964000000000000
2011-01-01	19.8445000000000000
2012-01-01	20.1621000000000000
2013-01-01	19.9516000000000000
2014-01-01	20.9930000000000020
2015-01-01	20.7776000000000000
2016-01-01	20.3559999999999980