Year	Percent
1976-01-01	22.414100000000000
1977-01-01	23.156800000000000
1978-01-01	20.169000000000000
1979-01-01	18.504300000000000
1980-01-01	24.677400000000000
1981-01-01	27.064200000000000
1982-01-01	23.722600000000000
1983-01-01	20.756300000000000
1984-01-01	20.022000000000002
1985-01-01	21.909100000000000
1986-01-01	23.518100000000000
1987-01-01	22.739900000000000
1988-01-01	22.571300000000000
1989-01-01	22.787500000000000
1990-01-01	22.390900000000000
1991-01-01	22.381200000000000
1992-01-01	21.976999999999997
1993-01-01	23.398900000000000
1994-01-01	25.860800000000000
1995-01-01	24.905300000000000
1996-01-01	26.665800000000000
1997-01-01	26.840500000000000
1998-01-01	31.101200000000000
1999-01-01	32.003300000000000
2000-01-01	31.369100000000000
2001-01-01	32.136200000000000
2002-01-01	34.095500000000000
2003-01-01	31.348600000000000
2004-01-01	32.891900000000000
2005-01-01	37.188400000000000
2006-01-01	31.761000000000000
2007-01-01	33.510100000000000
2008-01-01	34.891000000000000
2009-01-01	38.222200000000000
2010-01-01	40.304800000000000
2011-01-01	39.258900000000000
2012-01-01	40.050500000000000
2013-01-01	38.448900000000000
2014-01-01	40.151900000000000
2015-01-01	42.355300000000000
2016-01-01	42.183000000000000