Year	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