Annual Percent of Total
1960-01-01 36.7076257134379
1961-01-01 36.5868891992470
1962-01-01 36.1909740674513
1963-01-01 35.6053592841829
1964-01-01 34.9688141064969
1965-01-01 34.3429735991435
1966-01-01 33.7331797959365
1967-01-01 33.0578987600371
1968-01-01 32.3574377645186
1969-01-01 31.6533385688807
1970-01-01 30.9599899612301
1971-01-01 30.1098961277842
1972-01-01 29.2983143365785
1973-01-01 28.6335774376448
1974-01-01 28.1275152217131
1975-01-01 27.7110603227370
1976-01-01 27.1452122627879
1977-01-01 26.5775444459136
1978-01-01 26.0304106492230
1979-01-01 25.5037050871236
1980-01-01 24.9908813170588
1981-01-01 25.0022853478009
1982-01-01 24.9656644046135
1983-01-01 24.9309514650392
1984-01-01 24.9205623483447
1985-01-01 24.9319654903387
1986-01-01 25.0809654364974
1987-01-01 25.1410047278056
1988-01-01 25.2148397985550
1989-01-01 25.3433886696385
1990-01-01 25.4904032537887
1991-01-01 25.3531665919663
1992-01-01 25.1898242462925
1993-01-01 24.9979542009720
1994-01-01 24.7382064483760
1995-01-01 24.3925535198227
1996-01-01 24.2177043654678
1997-01-01 23.8597294410183
1998-01-01 23.3980482093179
1999-01-01 22.9030829868798
2000-01-01 22.4000992275937
2001-01-01 21.9840630148227
2002-01-01 21.5316602624861
2003-01-01 21.0491936595868
2004-01-01 20.5331499094427
2005-01-01 19.9974115902372
2006-01-01 19.5766846579035
2007-01-01 19.1378869468428
2008-01-01 18.6995117251607
2009-01-01 18.2646738477118
2010-01-01 17.8363968589089
2011-01-01 17.6157391973045
2012-01-01 17.3966708426500
2013-01-01 17.2040989740326
2014-01-01 17.0409152406169
2015-01-01 16.8953948586760
2016-01-01 16.8711035145818
2017-01-01 16.8300480437048