Year	Percent of Total
1960-01-01	39.1935576018438
1961-01-01	39.3493102656398
1962-01-01	39.6913591701479
1963-01-01	40.0691994421564
1964-01-01	40.2940421000766
1965-01-01	40.3075276205709
1966-01-01	40.4310863674032
1967-01-01	40.2908525079510
1968-01-01	40.0047310020881
1969-01-01	39.7313276384103
1970-01-01	39.5338644847813
1971-01-01	39.4280682135847
1972-01-01	39.3215469592391
1973-01-01	39.1972281671968
1974-01-01	38.9934621264857
1975-01-01	38.6712327825624
1976-01-01	38.2477220708989
1977-01-01	37.7321810199456
1978-01-01	37.1365246877011
1979-01-01	36.4937406723532
1980-01-01	35.8341064091696
1981-01-01	35.1164431524629
1982-01-01	34.4487552177134
1983-01-01	33.8184697274929
1984-01-01	33.2203722155371
1985-01-01	32.6686738999552
1986-01-01	32.3000803998694
1987-01-01	31.9712403898160
1988-01-01	31.6784275843518
1989-01-01	31.3923366919449
1990-01-01	31.0793070092347
1991-01-01	30.9362040374104
1992-01-01	30.6229779664106
1993-01-01	30.2159429604423
1994-01-01	29.8139914506120
1995-01-01	29.4532268917329
1996-01-01	28.8261531026030
1997-01-01	28.3603479546666
1998-01-01	27.9422236678816
1999-01-01	27.4190732772795
2000-01-01	26.7364131504397
2001-01-01	26.0771839483634
2002-01-01	25.2794909147424
2003-01-01	24.4096307524025
2004-01-01	23.5945118321685
2005-01-01	22.9047739180198
2006-01-01	22.3844606602020
2007-01-01	21.9425303236333
2008-01-01	21.5884072703591
2009-01-01	21.3079619774738
2010-01-01	21.0888483515480
2011-01-01	20.9280520763469
2012-01-01	20.8369997507668
2013-01-01	20.7930610151724
2014-01-01	20.7585214497992
2015-01-01	20.7077261195795
2016-01-01	20.6745810891302
2017-01-01	20.6015602052052