Year	Ratio
1990-01-01	0.191890001296997
1998-01-01	0.677460014820099
1999-01-01	0.620760023593903
2002-01-01	0.640869975090027
2011-01-01	0.362150013446808
2013-01-01	0.780439972877502
2015-01-01	0.769850015640259