Year	Percent
1980-01-01	8.18
1981-01-01	8.38
1982-01-01	9.03
1983-01-01	9.87
1984-01-01	10.51
1985-01-01	11.30
1986-01-01	12.19
1987-01-01	12.68
1988-01-01	13.89
1989-01-01	14.79
1990-01-01	14.79
1991-01-01	17.61
1992-01-01	18.75
1993-01-01	21.02
1994-01-01	21.11
1995-01-01	50.30
1996-01-01	54.50
1997-01-01	58.41
1998-01-01	62.63
1999-01-01	64.37
2000-01-01	62.45
2001-01-01	59.87
2002-01-01	55.63
2003-01-01	57.82
2004-01-01	58.85
2005-01-01	64.09
2006-01-01	63.62
2007-01-01	61.97
2008-01-01	59.42
2009-01-01	62.20
2010-01-01	64.63
2011-01-01	67.50
2012-01-01	72.43
2013-01-01	68.26
2014-01-01	77.32
2015-01-01	71.27
2016-01-01	71.17