Annual Percent of Total
1960-01-01 42.6302763237773
1961-01-01 41.5996934391213
1962-01-01 40.6889983186973
1963-01-01 39.9411306401250
1964-01-01 39.3093020433191
1965-01-01 38.6924816218976
1966-01-01 38.5495089044130
1967-01-01 38.1468129438698
1968-01-01 37.5969488363128
1969-01-01 37.0311668677697
1970-01-01 36.5200393676234
1971-01-01 35.8249595498277
1972-01-01 35.1548138230318
1973-01-01 34.5646199579688
1974-01-01 34.0536132558341
1975-01-01 33.5969406723181
1976-01-01 33.2058021493613
1977-01-01 32.8656726640951
1978-01-01 32.4894490186940
1979-01-01 32.0480015691449
1980-01-01 31.5558600620955
1981-01-01 31.2572164421895
1982-01-01 30.9380460918748
1983-01-01 30.5528338278842
1984-01-01 30.0965978491003
1985-01-01 29.5856964417085
1986-01-01 29.1078876006612
1987-01-01 28.6239663371661
1988-01-01 28.1247930052328
1989-01-01 27.6302332051293
1990-01-01 27.1669639494311
1991-01-01 26.7509426067840
1992-01-01 26.3717213846017
1993-01-01 26.0194727366781
1994-01-01 25.6623809404027
1995-01-01 25.2754942825061
1996-01-01 25.0240366260105
1997-01-01 24.7035588420651
1998-01-01 24.3228515579402
1999-01-01 23.9297782296667
2000-01-01 23.5609538851565
2001-01-01 23.2827540252959
2002-01-01 23.0374486173442
2003-01-01 22.8059910204401
2004-01-01 22.5521461280562
2005-01-01 22.2610405962290
2006-01-01 21.9777940104599
2007-01-01 21.6844340229698
2008-01-01 21.3598041430617
2009-01-01 21.0016769846801
2010-01-01 20.6191633261074
2011-01-01 20.2662595792159
2012-01-01 19.8756158088434
2013-01-01 19.4599052300756
2014-01-01 19.0492608093808
2015-01-01 18.6665153217658
2016-01-01 18.2685583560961
2017-01-01 17.9365411720192