Year	Percent of Total
1960-01-01	9.80625630113482
1961-01-01	9.95044872002198
1962-01-01	10.09795878793390
1963-01-01	10.24917113748270
1964-01-01	10.40389095637410
1965-01-01	10.56649672961500
1966-01-01	10.77262849952460
1967-01-01	10.97321296501190
1968-01-01	11.17141744012440
1969-01-01	11.37052854887820
1970-01-01	11.56778834274070
1971-01-01	11.79046188411200
1972-01-01	11.99585460036740
1973-01-01	12.18712578026270
1974-01-01	12.36785243905920
1975-01-01	12.53806705834650
1976-01-01	12.76260981259500
1977-01-01	12.98189184688480
1978-01-01	13.16788391473570
1979-01-01	13.27745481924370
1980-01-01	13.28919325229070
1981-01-01	13.25492658012970
1982-01-01	13.12174662924160
1983-01-01	12.94969218839860
1984-01-01	12.82399812220150
1985-01-01	12.79344311944080
1986-01-01	12.90596754207010
1987-01-01	13.09513133752380
1988-01-01	13.32993593571270
1989-01-01	13.56320782354200
1990-01-01	13.76740914033150
1991-01-01	14.00137576037040
1992-01-01	14.20839100734410
1993-01-01	14.39274465877010
1994-01-01	14.56534456253070
1995-01-01	14.73228757827270
1996-01-01	14.94695475775310
1997-01-01	15.14218922000930
1998-01-01	15.32665426569460
1999-01-01	15.50979299715320
2000-01-01	15.70036960320200
2001-01-01	15.91617154897870
2002-01-01	16.13280535568500
2003-01-01	16.34199612024280
2004-01-01	16.52953194498480
2005-01-01	16.68860682289990
2006-01-01	16.86686172359280
2007-01-01	17.01227202573700
2008-01-01	17.14871685799960
2009-01-01	17.31164993212420
2010-01-01	17.52730145031410
2011-01-01	17.78315933464560
2012-01-01	18.09520473027800
2013-01-01	18.44386839800160
2014-01-01	18.79718933908380
2015-01-01	19.13507215366120
2016-01-01	19.46344529254100
2017-01-01	19.77001655739730