Year	Percent of Total
1960-01-01	32.8868740290163
1961-01-01	33.1149811927563
1962-01-01	33.1028714285772
1963-01-01	32.9376291660689
1964-01-01	32.7439324479855
1965-01-01	32.5747103243872
1966-01-01	32.4177134411315
1967-01-01	32.2915140401587
1968-01-01	32.1562524777781
1969-01-01	31.9679047508855
1970-01-01	31.7218678627172
1971-01-01	31.4284898192922
1972-01-01	31.1425183449694
1973-01-01	30.8303079304304
1974-01-01	30.4438893594949
1975-01-01	29.9480995629386
1976-01-01	29.5869805087227
1977-01-01	29.0620117947506
1978-01-01	28.4211091495054
1979-01-01	27.7751677113843
1980-01-01	27.2014501914595
1981-01-01	26.5288982529224
1982-01-01	26.0022536967558
1983-01-01	25.5578439601098
1984-01-01	25.1097428459012
1985-01-01	24.6337779768658
1986-01-01	24.3051098014044
1987-01-01	23.9717187350392
1988-01-01	23.6479504271494
1989-01-01	23.3889335686235
1990-01-01	23.2312843493502
1991-01-01	23.1558222606546
1992-01-01	23.1101390422019
1993-01-01	23.0826289731079
1994-01-01	23.0525167948701
1995-01-01	23.0052441729597
1996-01-01	23.0215672512858
1997-01-01	23.0165692968855
1998-01-01	22.9611778516449
1999-01-01	22.8543494186030
2000-01-01	22.7152429943620
2001-01-01	22.4811428445677
2002-01-01	22.2640205934287
2003-01-01	22.0435303322743
2004-01-01	21.8036887216519
2005-01-01	21.5448250512955
2006-01-01	21.3138005364177
2007-01-01	21.0992473455353
2008-01-01	20.8980383678192
2009-01-01	20.6998201912255
2010-01-01	20.4974895093022
2011-01-01	20.4955000322517
2012-01-01	20.3953092198902
2013-01-01	20.2398790311602
2014-01-01	20.0884227122430
2015-01-01	19.9708442806334
2016-01-01	19.8219717376701
2017-01-01	19.7658090474387