Year	Percent of Total
1960-01-01	43.4250709264714
1961-01-01	43.2993730407523
1962-01-01	43.2731345373092
1963-01-01	43.2857583970906
1964-01-01	43.2380216383308
1965-01-01	43.0957042496833
1966-01-01	42.7786461270726
1967-01-01	42.4447601010101
1968-01-01	42.0818188848504
1969-01-01	41.6825974814140
1970-01-01	41.2441503472533
1971-01-01	40.8913591834340
1972-01-01	40.4562275933850
1973-01-01	39.9623212399737
1974-01-01	39.4410113152177
1975-01-01	38.8777946906115
1976-01-01	38.1310091996957
1977-01-01	37.3200686106346
1978-01-01	36.4628225410507
1979-01-01	35.6082036775106
1980-01-01	34.7866343509164
1981-01-01	33.7776804532888
1982-01-01	33.0223056537102
1983-01-01	32.4236798391937
1984-01-01	31.8557794273595
1985-01-01	31.2989022957210
1986-01-01	30.9145605952710
1987-01-01	30.5357800869629
1988-01-01	30.3751975901458
1989-01-01	30.6287240908340
1990-01-01	31.2657430730479
1991-01-01	30.9269466771658
1992-01-01	30.7700176830783
1993-01-01	30.6757413709285
1994-01-01	30.5093489870188
1995-01-01	30.2707181569975
1996-01-01	29.8011318559264
1997-01-01	29.5295797476170
1998-01-01	29.4473456813315
1999-01-01	29.4827143747480
2000-01-01	29.5164146248086
2001-01-01	29.3356219946624
2002-01-01	29.0566387684604
2003-01-01	28.7720664887219
2004-01-01	28.5711048415423
2005-01-01	28.4449822414933
2006-01-01	28.1115380782051
2007-01-01	27.7650715137720
2008-01-01	27.4021929539999
2009-01-01	27.0129620328913
2010-01-01	26.5980710112929
2011-01-01	26.1933367461006
2012-01-01	25.7736858964423
2013-01-01	25.3557409224730
2014-01-01	24.9476611883692
2015-01-01	24.5589103609780
2016-01-01	24.2197636758020
2017-01-01	23.8942477355605