Year	Ratio
1971-01-01	0.273429989814758
1972-01-01	0.289079993963242
1973-01-01	0.336650013923645
1974-01-01	0.370160013437271
1975-01-01	0.362040013074875
1976-01-01	0.359629988670349
1977-01-01	0.358869999647141
1978-01-01	0.359549999237061
1979-01-01	0.361129999160767
1980-01-01	0.368770003318787
1981-01-01	0.376780003309250
1982-01-01	0.384920001029968
1983-01-01	0.393620014190674
1984-01-01	0.402869999408722
1985-01-01	0.412690013647079
1986-01-01	0.423059999942780
1987-01-01	0.433690011501312
1988-01-01	0.474750012159348
1992-01-01	0.482989996671677
1993-01-01	0.471329987049103
1994-01-01	0.447380006313324
1995-01-01	0.609300017356873
2007-01-01	0.534300029277802
2008-01-01	0.556289970874786
2009-01-01	0.562139987945557
2010-01-01	0.577269971370697
2011-01-01	0.587729990482330
2012-01-01	0.592060029506683
2013-01-01	0.620310008525848
2014-01-01	0.621810019016266
2015-01-01	0.639509975910187