Year	Percent
1989-01-01	7.32
1990-01-01	7.46
1991-01-01	8.23
1992-01-01	8.69
1993-01-01	9.90
1994-01-01	11.39
1995-01-01	13.08
1996-01-01	14.68
1997-01-01	16.34
1998-01-01	17.94
1999-01-01	19.28
2000-01-01	19.69
2001-01-01	20.17
2002-01-01	21.19
2003-01-01	21.72
2004-01-01	22.95
2005-01-01	23.77
2006-01-01	22.91
2007-01-01	21.34
2008-01-01	20.96
2009-01-01	22.03
2010-01-01	22.03
2011-01-01	23.88
2012-01-01	24.85
2013-01-01	26.82
2014-01-01	29.09
2015-01-01	27.98
2016-01-01	27.86