Year	Percent of Total
1960-01-01	39.2030669202845
1961-01-01	39.2808324054143
1962-01-01	39.5804465196713
1963-01-01	39.9380686319463
1964-01-01	40.1591922008592
1965-01-01	40.1860648025126
1966-01-01	40.3498596411197
1967-01-01	40.2691461037568
1968-01-01	40.0599622388821
1969-01-01	39.8399857752745
1970-01-01	39.7006091478016
1971-01-01	39.6613832085121
1972-01-01	39.5996148029918
1973-01-01	39.5093786050665
1974-01-01	39.3111161900338
1975-01-01	38.9834446771378
1976-01-01	38.5286712399431
1977-01-01	37.9609794145519
1978-01-01	37.2945550013118
1979-01-01	36.5629982416763
1980-01-01	35.8022543867637
1981-01-01	34.9358884616560
1982-01-01	34.1295384001949
1983-01-01	33.3633788302509
1984-01-01	32.6254815148543
1985-01-01	31.9293501017366
1986-01-01	31.4467203709702
1987-01-01	30.9934127277622
1988-01-01	30.5820865831028
1989-01-01	30.2055935145122
1990-01-01	29.8409985707797
1991-01-01	29.6714164962742
1992-01-01	29.3675476329190
1993-01-01	28.9954107377829
1994-01-01	28.6321321513333
1995-01-01	28.3015250600958
1996-01-01	27.7219698003713
1997-01-01	27.2863977208247
1998-01-01	26.8874358270697
1999-01-01	26.3881537847663
2000-01-01	25.7427518762098
2001-01-01	25.1363274598418
2002-01-01	24.4155049820348
2003-01-01	23.6364785370444
2004-01-01	22.9056449541942
2005-01-01	22.2804964039243
2006-01-01	21.7713429241406
2007-01-01	21.3259729028619
2008-01-01	20.9568517754567
2009-01-01	20.6598997022400
2010-01-01	20.4263846731850
2011-01-01	20.2470702267921
2012-01-01	20.1355772719701
2013-01-01	20.0700624874386
2014-01-01	20.0134389869124
2015-01-01	19.9427025577091
2016-01-01	19.8901757758709
2017-01-01	19.8078332389021