Year	Percent of Total
1960-01-01	8.98916580183795
1961-01-01	9.24224527362867
1962-01-01	9.50660149051297
1963-01-01	9.77911488880079
1964-01-01	10.05292963360780
1965-01-01	10.32121063554910
1966-01-01	10.61804541682240
1967-01-01	10.88132728908390
1968-01-01	11.12173313302120
1969-01-01	11.35268653877150
1970-01-01	11.58257398464650
1971-01-01	11.80787467968760
1972-01-01	12.02350642492450
1973-01-01	12.23753259499180
1974-01-01	12.45921236499720
1975-01-01	12.69127703573670
1976-01-01	12.99641337106160
1977-01-01	13.30307688966690
1978-01-01	13.55106762975170
1979-01-01	13.66131243241770
1980-01-01	13.59998906531300
1981-01-01	13.38848938067430
1982-01-01	13.02843213773680
1983-01-01	12.61722338215350
1984-01-01	12.28825931278510
1985-01-01	12.11805787873490
1986-01-01	12.31687602770630
1987-01-01	12.60826448237630
1988-01-01	12.93866716652070
1989-01-01	13.23562125665460
1990-01-01	13.45655196922690
1991-01-01	13.69300175113500
1992-01-01	13.88267349914950
1993-01-01	14.03378068377040
1994-01-01	14.15583828806030
1995-01-01	14.25968213222270
1996-01-01	14.47500815107810
1997-01-01	14.67630004087680
1998-01-01	14.85444028270030
1999-01-01	14.99687949971310
2000-01-01	15.09639272908430
2001-01-01	15.26181319314640
2002-01-01	15.36557501904040
2003-01-01	15.43647004581760
2004-01-01	15.51326183151670
2005-01-01	15.61792957195610
2006-01-01	15.71930380750720
2007-01-01	15.83729944282090
2008-01-01	15.95187605574140
2009-01-01	16.03812935149140
2010-01-01	16.09169769053490
2011-01-01	16.35548226728810
2012-01-01	16.59048050575880
2013-01-01	16.83125379698240
2014-01-01	17.12545225450880
2015-01-01	17.49568808019280
2016-01-01	18.01166192176770
2017-01-01	18.57721585601650