Year	Percent
1970-01-01	54.17857015
1971-01-01	54.16430178
1972-01-01	51.85469184
1973-01-01	57.43762535
1974-01-01	54.30805043
1975-01-01	53.64805049
1976-01-01	39.94080345
1977-01-01	49.37723642
1978-01-01	48.91418791
1979-01-01	55.82434441
1980-01-01	57.53590345
1981-01-01	58.08622600
1982-01-01	58.04236664
1983-01-01	70.08762957
1984-01-01	61.69322568
1985-01-01	53.88073312
1986-01-01	43.35857072
1987-01-01	35.34249654
1988-01-01	43.61184735
1989-01-01	41.72802256
1990-01-01	53.65681415
1991-01-01	52.43592825
1992-01-01	53.30348042
1993-01-01	34.14699927
1994-01-01	31.40460629
1995-01-01	21.37134014
1996-01-01	60.30898375
1997-01-01	59.88563530
1998-01-01	67.83828058
1999-01-01	27.60496365
2000-01-01	22.65570574
2001-01-01	25.50542667
2002-01-01	24.41295197
2003-01-01	28.04103962
2004-01-01	13.01397033
2005-01-01	23.25435771
2006-01-01	18.16675758
2007-01-01	17.22810168
2008-01-01	19.42424014
2009-01-01	18.96848834
2010-01-01	18.74698520