Year	Percent of Total
1960-01-01	21.1819904128575
1961-01-01	21.4861974351139
1962-01-01	21.7696747457928
1963-01-01	22.0121497835685
1964-01-01	22.1889261560455
1965-01-01	22.2924573162790
1966-01-01	22.4186944789558
1967-01-01	22.4766401278173
1968-01-01	22.4560348267299
1969-01-01	22.3600055692648
1970-01-01	22.1966743997080
1971-01-01	21.9691081332219
1972-01-01	21.6599102296995
1973-01-01	21.2963095932195
1974-01-01	20.9078302566424
1975-01-01	20.5159569809850
1976-01-01	20.1060679148764
1977-01-01	19.7549642307949
1978-01-01	19.4367897904302
1979-01-01	19.1102817340107
1980-01-01	18.7568330778655
1981-01-01	18.4077569829569
1982-01-01	18.0296797024361
1983-01-01	17.6679760747868
1984-01-01	17.3783129895160
1985-01-01	17.1896294196531
1986-01-01	17.0951484541563
1987-01-01	17.0675706994217
1988-01-01	17.1103769398960
1989-01-01	17.2099463603967
1990-01-01	17.3555688845468
1991-01-01	17.5156334120181
1992-01-01	17.7153967613198
1993-01-01	17.9529245734735
1994-01-01	18.2025330924651
1995-01-01	18.4332192410125
1996-01-01	18.6186440063865
1997-01-01	18.7473510264921
1998-01-01	18.8357877383857
1999-01-01	18.9005755202174
2000-01-01	18.9439192117459
2001-01-01	18.9292091286194
2002-01-01	18.8925147500935
2003-01-01	18.8273771466639
2004-01-01	18.7336079270681
2005-01-01	18.6225815892819
2006-01-01	18.4126868204333
2007-01-01	18.2007574959661
2008-01-01	17.9998144731553
2009-01-01	17.8161880716291
2010-01-01	17.6440127665691
2011-01-01	17.3985125235363
2012-01-01	17.1416657431530
2013-01-01	16.8778145142192
2014-01-01	16.6187921972404
2015-01-01	16.3778516112298
2016-01-01	16.4164120698849
2017-01-01	16.4430847280424