Year	Ratio
1973-01-01	0.658869981765747
1977-01-01	0.464020013809204
1978-01-01	0.401109993457794
1979-01-01	0.381779998540878
1980-01-01	0.371919989585876
1981-01-01	0.373100012540817
1982-01-01	0.393500000238419
1983-01-01	0.431980013847351
1985-01-01	0.449880003929138
1986-01-01	0.482749998569489
1987-01-01	0.485749989748001
1990-01-01	0.564670026302338
1991-01-01	0.559449970722198
1992-01-01	0.596530020236969
1993-01-01	0.607169985771179
1994-01-01	0.590659976005554
1995-01-01	0.607590019702911
1999-01-01	0.611599981784821
2000-01-01	0.612590014934540
2001-01-01	0.625029981136322
2002-01-01	0.648729979991913
2004-01-01	0.693889975547791
2005-01-01	0.687960028648376
2006-01-01	0.714479982852936
2007-01-01	0.726429998874664
2008-01-01	0.745999991893768
2009-01-01	0.784680008888245
2010-01-01	0.814589977264404
2011-01-01	0.862800002098084
2012-01-01	0.888069987297058
2013-01-01	0.899999976158142
2014-01-01	0.905870020389557
2015-01-01	0.918529987335205