Year	Ratio
1970-01-01	0.953459978103638
1971-01-01	0.957899987697601
1972-01-01	0.958940029144287
1973-01-01	0.956900000572205
1974-01-01	0.959020018577576
1975-01-01	0.953400015830994
1976-01-01	0.964079976081848
1977-01-01	0.961359977722168
1978-01-01	0.960560023784637
1979-01-01	0.959839999675751
1980-01-01	0.960609972476959
1981-01-01	0.959999978542328
1982-01-01	0.961099982261658
1983-01-01	0.954659998416901
1984-01-01	0.948159992694855
1985-01-01	0.951640009880066
1986-01-01	0.952820003032684
1987-01-01	0.952130019664764
1988-01-01	0.959150016307831
1989-01-01	0.966750025749207
1990-01-01	0.962930023670197
1999-01-01	0.966120004653931
2000-01-01	0.967170000076294
2001-01-01	0.966849982738495
2002-01-01	0.965610027313232
2003-01-01	0.965210020542145
2004-01-01	0.968029975891113
2005-01-01	0.965409994125366
2006-01-01	0.967490017414093
2007-01-01	0.967559993267059
2008-01-01	0.964559972286224
2009-01-01	0.964349985122681
2010-01-01	0.962559998035431
2011-01-01	0.969020009040833
2012-01-01	0.968590021133423
2013-01-01	0.970979988574982
2014-01-01	0.974489986896515
2015-01-01	0.973489999771118