Year	Ratio
1973-01-01	0.511510014533997
1977-01-01	0.679740011692047
1978-01-01	0.688019990921021
1979-01-01	0.694599986076355
1981-01-01	0.736790001392365
1982-01-01	0.749979972839355
1983-01-01	0.740909993648529
1984-01-01	0.750899970531464
1985-01-01	0.772400021553040
1986-01-01	0.777869999408722
1987-01-01	0.775879979133606
1988-01-01	0.771130025386810
1989-01-01	0.767400026321411
1990-01-01	0.756269991397858
1991-01-01	0.739400029182434
1992-01-01	0.741060018539429
1993-01-01	0.728500008583069
1994-01-01	0.715179979801178
1995-01-01	0.711059987545013
1998-01-01	0.734210014343262
1999-01-01	0.739859998226166
2000-01-01	0.754419982433319
2001-01-01	0.770780026912689
2002-01-01	0.789569973945618
2004-01-01	0.828620016574860
2005-01-01	0.841109991073608
2006-01-01	0.858280003070831
2007-01-01	0.866400003433228
2008-01-01	0.877189993858337
2009-01-01	0.893239974975586
2010-01-01	0.897719979286194
2011-01-01	0.904659986495972
2012-01-01	0.908100008964539
2013-01-01	0.912400007247925
2014-01-01	0.918229997158051
2015-01-01	0.916660010814667