Year	Percent of Total
1960-01-01	37.9904255490646
1961-01-01	37.9859283671299
1962-01-01	37.8729915609625
1963-01-01	37.6392142496402
1964-01-01	37.3045376610199
1965-01-01	36.8863911484201
1966-01-01	36.7276951035428
1967-01-01	36.3710814280079
1968-01-01	35.8886743725670
1969-01-01	35.3948899599889
1970-01-01	34.9502077767292
1971-01-01	34.3607640426407
1972-01-01	33.9082523640335
1973-01-01	33.5040945485989
1974-01-01	33.0213181750500
1975-01-01	32.4105550094941
1976-01-01	31.7713989016872
1977-01-01	31.0037603450096
1978-01-01	30.1728632921580
1979-01-01	29.3963567868032
1980-01-01	28.7366906268280
1981-01-01	28.0890683292477
1982-01-01	27.5741270857218
1983-01-01	27.1426701200017
1984-01-01	26.7118328672830
1985-01-01	26.2447832828263
1986-01-01	25.8170210194828
1987-01-01	25.3870308465812
1988-01-01	24.9669924242290
1989-01-01	24.5666795291317
1990-01-01	24.1601175062542
1991-01-01	23.6631505651359
1992-01-01	23.1946279847347
1993-01-01	22.7440857984554
1994-01-01	22.3355051235611
1995-01-01	22.0203542825269
1996-01-01	21.7138603599957
1997-01-01	21.4828467198997
1998-01-01	21.2900998137574
1999-01-01	21.0518531208651
2000-01-01	20.7109607174014
2001-01-01	20.2752961590800
2002-01-01	19.6631077806678
2003-01-01	18.9495685251586
2004-01-01	18.2715567477422
2005-01-01	17.7072507688687
2006-01-01	17.0990467441449
2007-01-01	16.7025702172761
2008-01-01	16.4306292992426
2009-01-01	16.1351436690875
2010-01-01	15.7468504203559
2011-01-01	15.6067245616199
2012-01-01	15.3098788443616
2013-01-01	14.9357045591414
2014-01-01	14.6323810250247
2015-01-01	14.4777332102928
2016-01-01	14.2203345298702
2017-01-01	14.1294153977583