Year	Ratio
1978-01-01	0.313820004463196
1979-01-01	0.403409987688065
1980-01-01	0.291350007057190
1983-01-01	0.210889995098114
1999-01-01	0.579490005970001
2005-01-01	0.644500017166138
2006-01-01	0.595019996166229
2007-01-01	0.555220007896423
2008-01-01	0.578079998493195
2009-01-01	0.611320018768311
2010-01-01	0.610970020294189
2011-01-01	0.687860012054443
2012-01-01	0.692610025405884
2013-01-01	0.739049971103668