Year	Percent of Total
1960-01-01	30.3662886243023
1961-01-01	30.6424537372418
1962-01-01	30.5974066887843
1963-01-01	30.2920475786337
1964-01-01	29.8774521305172
1965-01-01	29.4312393575861
1966-01-01	28.8517447616420
1967-01-01	28.2293782400286
1968-01-01	27.5719971202774
1969-01-01	26.8920248791957
1970-01-01	26.2123698536661
1971-01-01	25.4202017548217
1972-01-01	24.7491647264374
1973-01-01	24.1606144024255
1974-01-01	23.5944961730194
1975-01-01	23.0288611262732
1976-01-01	22.7423111194062
1977-01-01	22.3451276879780
1978-01-01	21.9371926970350
1979-01-01	21.6559795051737
1980-01-01	21.5608055442500
1981-01-01	21.5390874715942
1982-01-01	21.7121642046552
1983-01-01	22.0082262066127
1984-01-01	22.3002625793226
1985-01-01	22.5189892832099
1986-01-01	22.7624453886544
1987-01-01	22.9275882207569
1988-01-01	23.0073359246745
1989-01-01	23.0018584450201
1990-01-01	22.9029118782888
1991-01-01	22.8414921359142
1992-01-01	22.5969527304588
1993-01-01	22.2257547937659
1994-01-01	21.8089673496770
1995-01-01	21.3833368808019
1996-01-01	20.6976672003370
1997-01-01	20.1342985637975
1998-01-01	19.6010773464620
1999-01-01	18.9806274973117
2000-01-01	18.2439323657666
2001-01-01	17.6486986950795
2002-01-01	16.9479066073417
2003-01-01	16.2248459285404
2004-01-01	15.6107843732046
2005-01-01	15.1731244897713
2006-01-01	14.9180173419979
2007-01-01	14.7501593117526
2008-01-01	14.6906337779574
2009-01-01	14.7386550256402
2010-01-01	14.8907913903466
2011-01-01	15.0880701436288
2012-01-01	15.4621786994793
2013-01-01	15.9432824713959
2014-01-01	16.4226389093182
2015-01-01	16.8326388070544
2016-01-01	17.2919704177376
2017-01-01	17.6054311475523