Year	Percent of Total
1960-01-01	7.92561806239002
1961-01-01	8.12917963613407
1962-01-01	8.33140105986956
1963-01-01	8.53261814556883
1964-01-01	8.73900894315053
1965-01-01	8.95797330017713
1966-01-01	9.18159445049437
1967-01-01	9.40100874420565
1968-01-01	9.62793378686875
1969-01-01	9.87568595696938
1970-01-01	10.14882451587400
1971-01-01	10.43850437419230
1972-01-01	10.72390427352990
1973-01-01	10.98864873231660
1974-01-01	11.21046599780580
1975-01-01	11.37912856905980
1976-01-01	11.45967985039930
1977-01-01	11.50891068799560
1978-01-01	11.51728594430790
1979-01-01	11.46695501201700
1980-01-01	11.35361009036190
1981-01-01	11.20671546481600
1982-01-01	10.98427178285680
1983-01-01	10.73668366443380
1984-01-01	10.53327627906560
1985-01-01	10.41276713762310
1986-01-01	10.40415063093060
1987-01-01	10.46310121389630
1988-01-01	10.57490932051200
1989-01-01	10.71692848203030
1990-01-01	10.87855252413800
1991-01-01	11.15643660649640
1992-01-01	11.44608334915000
1993-01-01	11.73885693721020
1994-01-01	12.02257850766780
1995-01-01	12.28918971533130
1996-01-01	12.65108935288150
1997-01-01	12.98805778032040
1998-01-01	13.30476243786100
1999-01-01	13.60962807769970
2000-01-01	13.90847941150850
2001-01-01	14.33540312590590
2002-01-01	14.76061861021130
2003-01-01	15.18293954460470
2004-01-01	15.59422060986930
2005-01-01	15.98542813161210
2006-01-01	16.31908867438680
2007-01-01	16.61315589043370
2008-01-01	16.86718241338730
2009-01-01	17.08447310188300
2010-01-01	17.27096747138020
2011-01-01	17.56733458208290
2012-01-01	17.85094128035730
2013-01-01	18.12787630607730
2014-01-01	18.40426544796720
2015-01-01	18.68508959639500
2016-01-01	18.84398481698090
2017-01-01	19.00237242055060