Year	Ratio
1971-01-01	0.244179993867874
1972-01-01	0.261310011148453
1973-01-01	0.333070009946823
1974-01-01	0.390489995479584
1975-01-01	0.420109987258911
1976-01-01	0.430350005626678
1977-01-01	0.476040005683899
1978-01-01	0.458409994840622
1979-01-01	0.462859988212585
1980-01-01	0.469729989767075
1981-01-01	0.459589987993240
1982-01-01	0.561559975147247
1983-01-01	0.470739990472794
1984-01-01	0.474739998579025
1985-01-01	0.502979993820190
1986-01-01	0.489950001239777
1987-01-01	0.533630013465881
1988-01-01	0.550360023975372
1989-01-01	0.575940012931824
1990-01-01	0.602159976959229
1991-01-01	0.567399978637695
1992-01-01	0.593190014362335
1993-01-01	0.618350028991699
2003-01-01	0.752369999885559
2004-01-01	0.732079982757568
2005-01-01	0.712670028209686
2006-01-01	0.708689987659454
2007-01-01	0.685270011425018
2009-01-01	0.683120012283325
2010-01-01	0.679579973220825
2011-01-01	0.698620021343231
2012-01-01	0.728860020637512
2013-01-01	0.779810011386871
2014-01-01	0.844250023365021
2015-01-01	0.907809972763062
2016-01-01	0.967130005359650