Year	Percent
1960-01-01	16.2777
1961-01-01	16.2074
1962-01-01	19.3670
1963-01-01	20.3926
1964-01-01	22.4832
1965-01-01	20.6577
1966-01-01	21.7651
1967-01-01	22.8645
1968-01-01	22.5600
1969-01-01	23.5055
1970-01-01	18.2637
1971-01-01	18.2259
1972-01-01	18.3184
1973-01-01	21.0832
1974-01-01	24.5128
1975-01-01	27.1813
1976-01-01	29.0519
1977-01-01	28.9998
1978-01-01	30.1929
1979-01-01	30.9944
1980-01-01	30.4401
1981-01-01	30.9822
1982-01-01	31.8888
1983-01-01	31.8888
1984-01-01	31.8888
1985-01-01	31.8888
1986-01-01	31.8888
1987-01-01	32.7942
1988-01-01	34.1146
1989-01-01	36.9530
1990-01-01	36.5072
1991-01-01	34.8751
1992-01-01	33.3941
1993-01-01	34.9465
1994-01-01	35.3178
1995-01-01	35.3426
1996-01-01	34.4508
1997-01-01	36.1655
1998-01-01	37.4932
1999-01-01	38.4106
2000-01-01	41.0537
2001-01-01	42.3562
2002-01-01	44.3081
2003-01-01	43.4851
2004-01-01	43.0802
2005-01-01	43.2825
2006-01-01	44.0012
2007-01-01	45.0753
2008-01-01	46.7202
2009-01-01	49.8023
2010-01-01	52.8875
2011-01-01	56.2515
2012-01-01	55.9811
2013-01-01	56.9786
2014-01-01	56.5508
2015-01-01	57.5406
2016-01-01	57.0685