Year	Percent of Total
1960-01-01	7.21484272554527
1961-01-01	7.40115938670058
1962-01-01	7.60816606586487
1963-01-01	7.82998881755935
1964-01-01	8.05818280098721
1965-01-01	8.28899640245106
1966-01-01	8.53966663971962
1967-01-01	8.76723684332522
1968-01-01	8.98500202735056
1969-01-01	9.20946579501227
1970-01-01	9.44639740430278
1971-01-01	9.69088732386259
1972-01-01	9.93401815168834
1973-01-01	10.17181754493290
1974-01-01	10.39783405457320
1975-01-01	10.60714101946960
1976-01-01	10.83270265776690
1977-01-01	11.04817033198840
1978-01-01	11.21705654978640
1979-01-01	11.28766150178630
1980-01-01	11.23669136419890
1981-01-01	11.08905725258300
1982-01-01	10.83028107300160
1983-01-01	10.53263002828980
1984-01-01	10.29662329114860
1985-01-01	10.17855305830190
1986-01-01	10.26577641163290
1987-01-01	10.43645784627880
1988-01-01	10.65796615516490
1989-01-01	10.87956583685700
1990-01-01	11.07825853396790
1991-01-01	11.34867898474250
1992-01-01	11.60477567386460
1993-01-01	11.84731187490110
1994-01-01	12.07520795052660
1995-01-01	12.28903283801590
1996-01-01	12.57170974734690
1997-01-01	12.83000916003420
1998-01-01	13.06049079557090
1999-01-01	13.27195501941850
2000-01-01	13.46562024597290
2001-01-01	13.73238018738860
2002-01-01	13.97834661305130
2003-01-01	14.20135514525320
2004-01-01	14.38231270938770
2005-01-01	14.51455950340990
2006-01-01	14.66433846300240
2007-01-01	14.76259571448590
2008-01-01	14.84119652575110
2009-01-01	14.94959753827310
2010-01-01	15.11940389478510
2011-01-01	15.38490144833800
2012-01-01	15.71096752850900
2013-01-01	16.08557003162480
2014-01-01	16.48913973820090
2015-01-01	16.90900384476450
2016-01-01	17.39548600876970
2017-01-01	17.88263147242330