Year	Percent of Total
1960-01-01	25.9283233780143
1961-01-01	25.8630916612067
1962-01-01	25.6171256948623
1963-01-01	25.2710783660062
1964-01-01	24.9616551135896
1965-01-01	24.7590860749590
1966-01-01	24.5962429834949
1967-01-01	24.5465099443362
1968-01-01	24.5647843335202
1969-01-01	24.5619814340656
1970-01-01	24.4919325294242
1971-01-01	24.4798757780834
1972-01-01	24.3706664802446
1973-01-01	24.1963622518874
1974-01-01	24.0015093805644
1975-01-01	23.7984436747121
1976-01-01	23.5189541834524
1977-01-01	23.2263934941016
1978-01-01	22.9109158172962
1979-01-01	22.5603923328721
1980-01-01	22.1765576558047
1981-01-01	21.7041927331553
1982-01-01	21.2631792973003
1983-01-01	20.8379994593395
1984-01-01	20.4191222028153
1985-01-01	20.0151934516464
1986-01-01	19.7259650370012
1987-01-01	19.4407026755399
1988-01-01	19.1903833744733
1989-01-01	19.0136252573873
1990-01-01	18.9252899205022
1991-01-01	18.9460708364104
1992-01-01	19.0230678575613
1993-01-01	19.1503960815310
1994-01-01	19.3032085986436
1995-01-01	19.4591017392967
1996-01-01	19.5987488872030
1997-01-01	19.7298938388720
1998-01-01	19.8448067065304
1999-01-01	19.9326375211108
2000-01-01	19.9834999012083
2001-01-01	19.9650685529648
2002-01-01	19.9129612084771
2003-01-01	19.8274613324067
2004-01-01	19.7220920992368
2005-01-01	19.6121677830153
2006-01-01	19.4453325116037
2007-01-01	19.2986637986562
2008-01-01	19.1560815683585
2009-01-01	18.9955833426555
2010-01-01	18.8115626300943
2011-01-01	18.6736384041135
2012-01-01	18.4710635879000
2013-01-01	18.2515179430151
2014-01-01	18.0749569432667
2015-01-01	17.9623165038282
2016-01-01	17.8268610883907
2017-01-01	17.7737215201994