Year	Ratio
1970-01-01	0.931659996509552
1971-01-01	0.940779983997345
1972-01-01	0.950410008430481
1973-01-01	0.949790000915527
1974-01-01	0.956920027732849
1975-01-01	0.958360016345978
1976-01-01	0.967779994010925
1977-01-01	0.960370004177094
1978-01-01	0.965200006961823
1979-01-01	0.971880018711090
1980-01-01	1.011039972305300
1981-01-01	0.985289990901947
1982-01-01	0.976830005645752
1983-01-01	0.980499982833862
1984-01-01	0.992619991302490
1987-01-01	0.992340028285980
1988-01-01	0.994870007038116
1989-01-01	0.987850010395050
1991-01-01	0.980660021305084
1992-01-01	0.986410021781921
1993-01-01	0.981599986553192
1995-01-01	0.984250009059906
1996-01-01	0.973230004310608
1997-01-01	0.966139972209930
1998-01-01	0.968580007553101
1999-01-01	0.959469974040985
2000-01-01	0.953880012035370
2001-01-01	0.960169970989227
2002-01-01	0.948740005493164
2003-01-01	0.964540004730225
2004-01-01	0.967410027980804
2005-01-01	0.966040015220642
2006-01-01	0.965290009975433
2007-01-01	1.001659989356990
2008-01-01	0.965740025043488
2009-01-01	0.964839994907379
2010-01-01	0.954919993877411
2011-01-01	0.953230023384094
2012-01-01	0.952130019664764
2013-01-01	0.953610002994537
2014-01-01	0.957889974117279
2015-01-01	0.958630025386810
2016-01-01	0.961279988288879