Year	Percent
1968-01-01	99.9925
1969-01-01	99.9945
1970-01-01	99.9961
1971-01-01	99.8064
1972-01-01	99.5419
1973-01-01	93.1286
1974-01-01	94.2337
1975-01-01	82.1079
1976-01-01	78.4008
1977-01-01	77.6204
1978-01-01	75.8770
1979-01-01	76.7572
1980-01-01	75.6352
1981-01-01	74.3554
1982-01-01	70.3571
1983-01-01	68.9945
1984-01-01	69.9709
1985-01-01	76.6890
1986-01-01	78.1094
1987-01-01	79.7154
1988-01-01	80.5942
1989-01-01	75.6418
1990-01-01	72.2436
1991-01-01	73.3679
1992-01-01	73.3679
1993-01-01	73.3679
1994-01-01	73.3679
1995-01-01	73.3679
1996-01-01	73.3679
1997-01-01	73.3679
1998-01-01	73.3679
1999-01-01	73.3679
2000-01-01	73.3679
2001-01-01	73.3679
2002-01-01	73.3679
2003-01-01	73.3679
2004-01-01	73.3679
2005-01-01	57.5625
2006-01-01	57.5066
2007-01-01	59.5892
2008-01-01	63.5235
2009-01-01	64.3444
2010-01-01	64.7709
2011-01-01	65.9729
2012-01-01	67.7103