Year	Percent of Total
1960-01-01	36.2941127407904
1961-01-01	37.6036521418729
1962-01-01	38.8422280233934
1963-01-01	39.9477318617859
1964-01-01	40.8387683418966
1965-01-01	41.4703412159296
1966-01-01	41.9440266862668
1967-01-01	42.1353792804001
1968-01-01	42.1036546949511
1969-01-01	41.9458657854966
1970-01-01	41.7175668650147
1971-01-01	41.3076396973847
1972-01-01	40.9723606399542
1973-01-01	40.6591498955431
1974-01-01	40.2809807015415
1975-01-01	39.7954225926649
1976-01-01	39.2530852008788
1977-01-01	38.6173820848661
1978-01-01	37.9538419816469
1979-01-01	37.3758299877884
1980-01-01	36.9444203666538
1981-01-01	36.6459462042778
1982-01-01	36.4971744796103
1983-01-01	36.4780572995237
1984-01-01	36.5185744755125
1985-01-01	36.5664222287112
1986-01-01	36.8126174332613
1987-01-01	37.0196558607245
1988-01-01	37.1933776724668
1989-01-01	37.3373442786282
1990-01-01	37.4355632087704
1991-01-01	37.6315579287049
1992-01-01	37.7221981375285
1993-01-01	37.7263238652583
1994-01-01	37.6677795725016
1995-01-01	37.5604538415497
1996-01-01	37.1520443910850
1997-01-01	36.7166790135578
1998-01-01	36.2328650220096
1999-01-01	35.6520059434753
2000-01-01	34.9402262027615
2001-01-01	34.2654944293202
2002-01-01	33.4868926863175
2003-01-01	32.6173236113225
2004-01-01	31.7416938587265
2005-01-01	30.9564407000067
2006-01-01	30.5232770206350
2007-01-01	30.1822448995322
2008-01-01	29.9672348219237
2009-01-01	29.8768663234834
2010-01-01	29.8975699961105
2011-01-01	29.9827062102375
2012-01-01	30.1744978824149
2013-01-01	30.4485654687843
2014-01-01	30.7679226456153
2015-01-01	31.0993570601567
2016-01-01	31.5151751236707
2017-01-01	31.8440321337039