Year	Ratio
1979-01-01	0.2219599932432170
1980-01-01	0.1253799945116040
1981-01-01	0.0887700021266937
1982-01-01	0.1153400018811230
1983-01-01	0.0614800006151199
1984-01-01	0.1078500002622600
1986-01-01	0.1185399964451790
1988-01-01	0.1521099954843520
1990-01-01	0.1906599998474120
1991-01-01	0.1509699970483780
1992-01-01	0.1699299961328510
1999-01-01	0.1876100003719330
2000-01-01	0.1897500008344650
2006-01-01	0.2832199931144710
2008-01-01	0.3512200117111210
2009-01-01	0.4304299950599670
2010-01-01	0.3183499872684480
2012-01-01	0.3612000048160550