Year	Percent
1970-01-01	28.940046040
1971-01-01	29.585826490
1972-01-01	27.279710150
1973-01-01	22.080835030
1974-01-01	21.166140850
1975-01-01	26.327765360
1976-01-01	31.156670650
1977-01-01	27.422860650
1978-01-01	28.183041160
1979-01-01	27.114699860
1980-01-01	26.544713420
1981-01-01	29.432942360
1982-01-01	33.448756910
1983-01-01	29.629659970
1984-01-01	33.913220540
1985-01-01	38.375235410
1986-01-01	41.628151760
1987-01-01	42.867910900
1988-01-01	41.422870460
1989-01-01	35.835579680
1990-01-01	30.275518170
1991-01-01	34.406504090
1992-01-01	30.009766860
1993-01-01	21.598767480
1994-01-01	15.269912350
1995-01-01	26.759634910
1996-01-01	20.047167530
1997-01-01	23.062371780
1998-01-01	26.292839470
1999-01-01	10.294526330
2000-01-01	8.731726518
2001-01-01	9.762786583
2002-01-01	9.269399524
2003-01-01	10.691418820
2004-01-01	4.949476297
2005-01-01	8.813856580
2006-01-01	6.882815440
2007-01-01	6.509025428
2008-01-01	7.338281743
2009-01-01	7.167894778
2010-01-01	7.085169087