Year	Percent
1980-01-01	0.260
1981-01-01	0.330
1982-01-01	0.310
1983-01-01	0.470
1984-01-01	0.980
1985-01-01	1.470
1986-01-01	2.310
1987-01-01	3.630
1988-01-01	5.290
1989-01-01	5.070
1990-01-01	3.300
1991-01-01	1.865
1992-01-01	1.385
1993-01-01	3.270
1994-01-01	3.970
1995-01-01	3.540
1996-01-01	1.850
1997-01-01	3.300
1998-01-01	4.790
1999-01-01	5.315
2000-01-01	5.265
2001-01-01	6.120
2002-01-01	6.695
2003-01-01	6.550
2004-01-01	7.090
2005-01-01	4.380
2006-01-01	4.440
2007-01-01	5.070
2008-01-01	5.150
2009-01-01	5.835
2010-01-01	6.975
2011-01-01	6.240
2012-01-01	9.085
2013-01-01	7.480
2014-01-01	9.400
2015-01-01	7.050