Year	Percent
1960-01-01	16.9096
1961-01-01	18.0791
1962-01-01	17.5255
1963-01-01	18.3863
1964-01-01	17.8963
1965-01-01	19.2465
1966-01-01	22.0221
1967-01-01	23.0588
1968-01-01	25.2777
1969-01-01	26.8150
1970-01-01	34.8528
1971-01-01	35.4886
1972-01-01	33.0666
1973-01-01	29.4715
1974-01-01	20.8895
1975-01-01	19.5051
1976-01-01	23.0447
1977-01-01	27.1301
1978-01-01	30.3494
1979-01-01	31.1475
1980-01-01	30.5329
1981-01-01	30.8209
1982-01-01	41.5095
1983-01-01	52.0198
1984-01-01	62.7717
1985-01-01	74.3979
1986-01-01	76.0996
1987-01-01	70.2488
1988-01-01	45.5811
1989-01-01	41.2547
1990-01-01	37.4421
1991-01-01	35.3962
1992-01-01	34.2949
1993-01-01	36.0731
1994-01-01	30.4677
1995-01-01	32.7133
1996-01-01	32.5656
1997-01-01	34.0378
1998-01-01	33.8428
1999-01-01	32.8259
2000-01-01	28.6007
2001-01-01	28.4484
2002-01-01	26.7864
2003-01-01	28.8180
2004-01-01	23.3046
2005-01-01	19.7745
2006-01-01	18.1545
2007-01-01	15.4099
2008-01-01	13.4911
2009-01-01	12.4141
2010-01-01	11.2388