Year	Percent
1988-01-01	6.07
1989-01-01	6.18
1990-01-01	6.08
1991-01-01	6.55
1992-01-01	6.10
1993-01-01	7.49
1994-01-01	7.16
1995-01-01	8.18
1996-01-01	10.25
1997-01-01	13.20
1998-01-01	15.32
1999-01-01	17.54
2000-01-01	26.16
2001-01-01	29.43
2002-01-01	27.09
2003-01-01	30.08
2004-01-01	31.04
2005-01-01	34.84
2006-01-01	39.80
2007-01-01	36.68
2008-01-01	21.72
2009-01-01	26.29
2010-01-01	23.22
2011-01-01	16.42
2012-01-01	16.99