Year	Ratio
1971-01-01	0.426860004663467
1973-01-01	0.433180004358292
1974-01-01	0.441000014543533
1975-01-01	0.482289999723434
1977-01-01	0.378320008516312
1985-01-01	0.410910010337830
1986-01-01	0.397150009870529
1987-01-01	0.402709990739822
1999-01-01	0.460979998111725
2000-01-01	0.457639992237091
2001-01-01	0.472310006618500
2002-01-01	0.472689986228943
2003-01-01	0.467150002717972
2004-01-01	0.471179991960526
2011-01-01	0.623480021953583
2013-01-01	0.670069992542267
2014-01-01	0.689700007438660
2015-01-01	0.714070022106171