Year	Percent
1960-01-01	20.4488
1961-01-01	20.9815
1962-01-01	24.2995
1963-01-01	23.6315
1964-01-01	27.0276
1965-01-01	27.1286
1966-01-01	30.5387
1967-01-01	33.8078
1968-01-01	34.0452
1969-01-01	35.1226
1970-01-01	26.8462
1971-01-01	25.4508
1972-01-01	24.4768
1973-01-01	27.7924
1974-01-01	32.2397
1975-01-01	36.2662
1976-01-01	39.1865
1977-01-01	39.8183
1978-01-01	40.8547
1979-01-01	39.6381
1980-01-01	38.3005
1981-01-01	40.9697
1982-01-01	45.3056
1983-01-01	45.3056
1984-01-01	45.3056
1985-01-01	45.3056
1986-01-01	45.3056
1987-01-01	44.8043
1988-01-01	44.3761
1989-01-01	47.8258
1990-01-01	48.8776
1991-01-01	47.6301
1992-01-01	51.7069
1993-01-01	58.8717
1994-01-01	59.2560
1995-01-01	60.2905
1996-01-01	57.1421
1997-01-01	55.6794
1998-01-01	56.9798
1999-01-01	56.7432
2000-01-01	57.3861
2001-01-01	58.0663
2002-01-01	60.5734
2003-01-01	58.9197
2004-01-01	57.1990
2005-01-01	56.2415
2006-01-01	55.5488
2007-01-01	54.9919
2008-01-01	55.9578
2009-01-01	58.7459
2010-01-01	63.4131
2011-01-01	71.7664
2012-01-01	73.1085
2013-01-01	74.1021
2014-01-01	74.5144
2015-01-01	76.9741
2016-01-01	77.4412