Year	Percent
1960-01-01	32.740
1961-01-01	32.395
1962-01-01	33.115
1963-01-01	34.990
1964-01-01	35.530
1965-01-01	34.920
1966-01-01	36.220
1967-01-01	35.600
1968-01-01	38.730
1969-01-01	38.610
1970-01-01	43.140
1971-01-01	41.200
1972-01-01	45.535
1973-01-01	48.370
1974-01-01	46.730
1975-01-01	47.195
1976-01-01	47.435
1977-01-01	51.460
1978-01-01	56.630
1979-01-01	57.410
1980-01-01	58.745
1981-01-01	59.650
1982-01-01	58.945
1983-01-01	59.155
1984-01-01	57.510
1985-01-01	58.360
1986-01-01	59.160
1987-01-01	61.310
1988-01-01	69.860
1989-01-01	75.720
1990-01-01	76.955
1991-01-01	77.630
1992-01-01	80.290
1993-01-01	68.460
1994-01-01	72.930
1995-01-01	62.490
1996-01-01	68.430
1997-01-01	72.700
1998-01-01	53.565
1999-01-01	57.370
2000-01-01	81.290
2001-01-01	70.570
2002-01-01	70.010
2003-01-01	67.840
2004-01-01	66.690
2005-01-01	68.320
2006-01-01	72.050
2007-01-01	80.040
2008-01-01	90.090
2009-01-01	99.150
2010-01-01	95.500
2011-01-01	93.180
2012-01-01	94.040
2013-01-01	92.430
2014-01-01	90.010
2015-01-01	89.500