Year	Percent of Total
1960-01-01	29.7648173025196
1961-01-01	29.7921065822859
1962-01-01	29.7168021708847
1963-01-01	29.5695354200880
1964-01-01	29.3994340287663
1965-01-01	29.2287799553724
1966-01-01	29.0923405525328
1967-01-01	28.9359017728990
1968-01-01	28.7675547470665
1969-01-01	28.5766798954882
1970-01-01	28.3809823439771
1971-01-01	28.1339254346678
1972-01-01	27.8964245531300
1973-01-01	27.6569579095453
1974-01-01	27.3831551178561
1975-01-01	27.0689750712646
1976-01-01	26.8149633871747
1977-01-01	26.4917720398680
1978-01-01	26.1263126966815
1979-01-01	25.7611790220632
1980-01-01	25.4205013305722
1981-01-01	25.0732355870545
1982-01-01	24.7744197237198
1983-01-01	24.5032842292956
1984-01-01	24.2246016116288
1985-01-01	23.9231435978335
1986-01-01	23.6768210682371
1987-01-01	23.3972906331606
1988-01-01	23.1026769527936
1989-01-01	22.8238150645527
1990-01-01	22.5784502857978
1991-01-01	22.3785775411491
1992-01-01	22.2051979568720
1993-01-01	22.0465023414928
1994-01-01	21.8788003047124
1995-01-01	21.6890645777178
1996-01-01	21.5177266718507
1997-01-01	21.3198344599415
1998-01-01	21.1048281175432
1999-01-01	20.8902403905854
2000-01-01	20.6834250100900
2001-01-01	20.4565015878923
2002-01-01	20.2463396969087
2003-01-01	20.0445012855838
2004-01-01	19.8417569947772
2005-01-01	19.6355490575337
2006-01-01	19.4705257305608
2007-01-01	19.3019599527461
2008-01-01	19.1344580409802
2009-01-01	18.9729399743174
2010-01-01	18.8149501520620
2011-01-01	18.7014356549667
2012-01-01	18.5614841265466
2013-01-01	18.4150705991014
2014-01-01	18.2800623999305
2015-01-01	18.1628852346746
2016-01-01	18.0382080044300
2017-01-01	17.9447145598719