Year	Percent
1980-01-01	8.180
1981-01-01	8.380
1982-01-01	9.030
1983-01-01	9.870
1984-01-01	10.510
1985-01-01	11.300
1986-01-01	12.190
1987-01-01	12.680
1988-01-01	13.890
1989-01-01	14.790
1990-01-01	14.790
1991-01-01	17.610
1992-01-01	18.750
1993-01-01	21.020
1994-01-01	21.110
1995-01-01	22.950
1996-01-01	24.690
1997-01-01	14.035
1998-01-01	16.335
1999-01-01	32.590
2000-01-01	29.830
2001-01-01	25.020
2002-01-01	25.410
2003-01-01	26.800
2004-01-01	24.810
2005-01-01	28.480
2006-01-01	30.710
2007-01-01	25.500
2008-01-01	25.810
2009-01-01	27.020
2010-01-01	27.780
2011-01-01	25.970
2012-01-01	28.180
2013-01-01	30.250
2014-01-01	30.510
2015-01-01	8.870