Year	Percent
1980-01-01	1.400
1981-01-01	1.310
1982-01-01	1.165
1983-01-01	1.320
1984-01-01	1.520
1985-01-01	1.980
1986-01-01	2.360
1987-01-01	2.660
1988-01-01	2.600
1989-01-01	1.735
1990-01-01	2.810
1991-01-01	3.250
1992-01-01	3.200
1993-01-01	4.675
1994-01-01	4.110
1995-01-01	4.510
1996-01-01	4.360
1997-01-01	4.880
1998-01-01	5.230
1999-01-01	5.930
2000-01-01	5.310
2001-01-01	5.335
2002-01-01	5.945
2003-01-01	6.100
2004-01-01	6.710
2005-01-01	5.315
2006-01-01	6.200
2007-01-01	6.935
2008-01-01	5.220
2009-01-01	7.370
2010-01-01	8.940
2011-01-01	6.375
2012-01-01	9.430
2013-01-01	9.650
2014-01-01	8.935
2015-01-01	10.840