Year	Percent
1980-01-01	16.99
1981-01-01	17.40
1982-01-01	19.24
1983-01-01	22.29
1984-01-01	23.95
1985-01-01	26.95
1986-01-01	33.00
1987-01-01	37.71
1988-01-01	41.71
1989-01-01	40.94
1990-01-01	39.25
1991-01-01	34.67
1992-01-01	35.84
1993-01-01	38.09
1994-01-01	37.33
1995-01-01	40.04
1996-01-01	39.88
1997-01-01	39.60
1998-01-01	63.06
1999-01-01	66.91
2000-01-01	65.90
2001-01-01	66.67
2002-01-01	67.50
2003-01-01	68.55
2004-01-01	69.39
2005-01-01	74.26
2006-01-01	73.79
2007-01-01	72.34
2008-01-01	70.69
2009-01-01	71.26
2010-01-01	70.13
2011-01-01	72.24
2012-01-01	75.26
2013-01-01	75.26
2014-01-01	77.36
2015-01-01	74.92
2016-01-01	78.88