Year	Percent
1970-01-01	0.445
1971-01-01	0.435
1972-01-01	0.865
1973-01-01	0.680
1974-01-01	0.620
1975-01-01	0.710
1976-01-01	0.585
1977-01-01	0.635
1978-01-01	0.830
1979-01-01	0.690
1980-01-01	0.870
1981-01-01	0.900
1982-01-01	0.815
1983-01-01	0.780
1984-01-01	0.830
1985-01-01	0.795
1986-01-01	0.720
1987-01-01	0.810
1988-01-01	1.010
1989-01-01	1.080
1990-01-01	1.160
1991-01-01	0.960
1992-01-01	0.890
1993-01-01	0.910
1994-01-01	1.050
1995-01-01	1.000
1996-01-01	0.965
1997-01-01	0.985
1998-01-01	1.085
1999-01-01	1.150
2000-01-01	0.990
2001-01-01	1.040
2002-01-01	1.035
2003-01-01	1.270
2004-01-01	1.620
2005-01-01	1.700
2006-01-01	1.770
2007-01-01	1.910
2008-01-01	1.775
2009-01-01	1.870
2010-01-01	1.790
2011-01-01	2.000
2012-01-01	2.020
2013-01-01	1.950
2014-01-01	1.795
2015-01-01	2.015