Year	Percent
1980-01-01	4.025
1981-01-01	4.050
1982-01-01	3.250
1983-01-01	4.170
1984-01-01	4.780
1985-01-01	4.840
1986-01-01	4.700
1987-01-01	4.590
1988-01-01	4.320
1989-01-01	5.500
1990-01-01	5.350
1991-01-01	5.420
1992-01-01	5.715
1993-01-01	5.420
1994-01-01	5.510
1995-01-01	5.770
1996-01-01	5.020
1997-01-01	4.905
1998-01-01	4.580
1999-01-01	3.975
2000-01-01	4.535
2001-01-01	4.760
2002-01-01	3.845
2003-01-01	3.255
2004-01-01	3.820
2005-01-01	2.870
2006-01-01	2.980
2007-01-01	2.320
2008-01-01	2.315
2009-01-01	4.555
2010-01-01	6.650
2011-01-01	5.365
2012-01-01	5.110
2013-01-01	5.375
2014-01-01	4.260
2015-01-01	3.980