Year	Percent of Total
1960-01-01	23.1460829261149
1961-01-01	23.2874348340218
1962-01-01	23.2895038201605
1963-01-01	23.2232721942027
1964-01-01	23.2050043396963
1965-01-01	23.2794340846832
1966-01-01	23.4962303171923
1967-01-01	23.6993935100536
1968-01-01	23.8950122091972
1969-01-01	24.0571764101024
1970-01-01	24.1588634910780
1971-01-01	24.1528585954963
1972-01-01	24.1100126280259
1973-01-01	24.0018474381377
1974-01-01	23.7981557225054
1975-01-01	23.4906611578496
1976-01-01	23.0949854486620
1977-01-01	22.6290115427779
1978-01-01	22.1028418324929
1979-01-01	21.5529409330721
1980-01-01	21.0165807717788
1981-01-01	20.5427985112387
1982-01-01	20.1138388638389
1983-01-01	19.7383825570477
1984-01-01	19.4162258704812
1985-01-01	19.1486167168068
1986-01-01	19.0451332301534
1987-01-01	18.9525517619643
1988-01-01	18.8961437470302
1989-01-01	18.8993125776058
1990-01-01	18.9621674889838
1991-01-01	19.0161652587964
1992-01-01	19.1264933722922
1993-01-01	19.2661524216809
1994-01-01	19.3875497699209
1995-01-01	19.4600495588687
1996-01-01	19.4491283857100
1997-01-01	19.3937690328976
1998-01-01	19.2987274151695
1999-01-01	19.1771906003003
2000-01-01	19.0359365144332
2001-01-01	18.8486708973251
2002-01-01	18.6288357942894
2003-01-01	18.3948374680444
2004-01-01	18.1715996599299
2005-01-01	17.9792778360567
2006-01-01	17.8295897914308
2007-01-01	17.7280164052036
2008-01-01	17.6611524081016
2009-01-01	17.5984107293244
2010-01-01	17.5222131989744
2011-01-01	17.5787183333662
2012-01-01	17.5698397191112
2013-01-01	17.5378609680434
2014-01-01	17.5364818883861
2015-01-01	17.5846735053002
2016-01-01	17.6187995806080
2017-01-01	17.7112047104946