Year	Percent of Total
1960-01-01	29.2828928720366
1961-01-01	29.2087551430260
1962-01-01	29.1633757715238
1963-01-01	29.1471359143656
1964-01-01	29.1435032212196
1965-01-01	29.1143672223898
1966-01-01	29.2113884863283
1967-01-01	29.1673946744141
1968-01-01	29.0128251486426
1969-01-01	28.8349582524092
1970-01-01	28.7094763128092
1971-01-01	28.3540974659065
1972-01-01	28.0913043694673
1973-01-01	27.8931755710092
1974-01-01	27.6773104252370
1975-01-01	27.3934826305859
1976-01-01	27.2071049487017
1977-01-01	26.9065038288613
1978-01-01	26.5309283872427
1979-01-01	26.1459457122386
1980-01-01	25.7750576729825
1981-01-01	25.3349558396303
1982-01-01	24.9347327536345
1983-01-01	24.5502372515632
1984-01-01	24.1327699403278
1985-01-01	23.6489135578071
1986-01-01	23.1325941797742
1987-01-01	22.5454665436060
1988-01-01	21.8892316629492
1989-01-01	21.2014706831351
1990-01-01	20.5249460808431
1991-01-01	19.9019168965516
1992-01-01	19.3144344975252
1993-01-01	18.7696643539192
1994-01-01	18.2570634584666
1995-01-01	17.7656263932014
1996-01-01	17.4081673059342
1997-01-01	17.0310442295642
1998-01-01	16.6531383569344
1999-01-01	16.3109226169784
2000-01-01	16.0297657670116
2001-01-01	15.8260181058132
2002-01-01	15.6882428663952
2003-01-01	15.6041038177046
2004-01-01	15.5300757921436
2005-01-01	15.4275481195182
2006-01-01	15.4602695804915
2007-01-01	15.4273423065779
2008-01-01	15.3204452943969
2009-01-01	15.1561410710225
2010-01-01	14.9559706283729
2011-01-01	14.7904018039910
2012-01-01	14.6131842525025
2013-01-01	14.4359143339735
2014-01-01	14.2592211298682
2015-01-01	14.0768709579609
2016-01-01	13.8617403036187
2017-01-01	13.6348146755518