Year	Ratio
1972-01-01	0.264699995517731
1973-01-01	0.242840006947517
1993-01-01	0.208419993519783
1994-01-01	0.203130006790161
1995-01-01	0.183939993381500
1996-01-01	0.181439995765686
1997-01-01	0.181559994816780
2000-01-01	0.319409996271133
2001-01-01	0.363090008497238
2002-01-01	0.395190000534058
2004-01-01	0.449440002441406
2005-01-01	0.455549985170364
2006-01-01	0.464379996061325
2007-01-01	0.489809989929199
2008-01-01	0.513109982013702
2009-01-01	0.560289978981018
2010-01-01	0.594690024852753
2011-01-01	0.615409970283508
2015-01-01	0.820819973945618