Year	Percent of Total
1960-01-01	25.2077830198461
1961-01-01	24.9658270313546
1962-01-01	24.6500260466741
1963-01-01	24.3098202219714
1964-01-01	24.0140790057814
1965-01-01	23.7908311381673
1966-01-01	23.6587319010768
1967-01-01	23.5442133619441
1968-01-01	23.4527959740801
1969-01-01	23.3728921184718
1970-01-01	23.2909525208766
1971-01-01	23.1754364679322
1972-01-01	23.0769539044425
1973-01-01	22.9678899667706
1974-01-01	22.8106610460269
1975-01-01	22.5866721288064
1976-01-01	22.3458440581847
1977-01-01	22.0372980815355
1978-01-01	21.6710602795864
1979-01-01	21.2669918399315
1980-01-01	20.8351963184616
1981-01-01	20.3637525076591
1982-01-01	19.8661851847298
1983-01-01	19.3559974427725
1984-01-01	18.8614749871874
1985-01-01	18.4099191219502
1986-01-01	17.9791528542383
1987-01-01	17.6465921231155
1988-01-01	17.3935629517256
1989-01-01	17.1904277301344
1990-01-01	17.0289907928533
1991-01-01	17.0362303265160
1992-01-01	17.0503224309456
1993-01-01	17.0980950315003
1994-01-01	17.2050380958119
1995-01-01	17.3695855909297
1996-01-01	17.5883848475507
1997-01-01	17.8129495912148
1998-01-01	18.0435399053539
1999-01-01	18.2678557939514
2000-01-01	18.4694658160703
2001-01-01	18.5578852950936
2002-01-01	18.6522076659828
2003-01-01	18.7258584049506
2004-01-01	18.7531893415237
2005-01-01	18.7279566453486
2006-01-01	18.6341575771958
2007-01-01	18.5055385261712
2008-01-01	18.3476830256494
2009-01-01	18.1623925824314
2010-01-01	17.9497210002657
2011-01-01	17.8105609781917
2012-01-01	17.5685569968595
2013-01-01	17.2852364665260
2014-01-01	17.0330093288846
2015-01-01	16.8431599866050
2016-01-01	16.5943377562865
2017-01-01	16.4851939051384