Year	Percent
1981-01-01	8.22
1982-01-01	8.69
1983-01-01	9.37
1984-01-01	10.09
1985-01-01	10.59
1986-01-01	11.18
1987-01-01	11.84
1988-01-01	12.59
1989-01-01	13.02
1990-01-01	13.82
1991-01-01	14.35
1992-01-01	15.55
1993-01-01	17.19
1994-01-01	18.06
1995-01-01	22.39
1996-01-01	24.17
1997-01-01	25.23
1998-01-01	25.35
1999-01-01	26.05
2000-01-01	25.56
2001-01-01	25.87
2002-01-01	26.36
2003-01-01	28.26
2004-01-01	30.00
2005-01-01	34.59
2006-01-01	33.67
2007-01-01	31.86
2008-01-01	31.64
2009-01-01	29.62
2010-01-01	30.85
2011-01-01	29.77
2012-01-01	30.02
2013-01-01	30.25
2014-01-01	30.26
2015-01-01	29.31
2016-01-01	28.96