Year	Percent of Total
1960-01-01	40.3636222053864
1961-01-01	40.4460912875051
1962-01-01	40.5961245712091
1963-01-01	40.7448483001511
1964-01-01	40.7839915771297
1965-01-01	40.6814984629813
1966-01-01	40.7474832556686
1967-01-01	40.6447579818906
1968-01-01	40.4447420478616
1969-01-01	40.2485615847913
1970-01-01	40.1044073911217
1971-01-01	40.2092375140446
1972-01-01	40.3200312883518
1973-01-01	40.4381974929920
1974-01-01	40.5475033975122
1975-01-01	40.6365049391756
1976-01-01	41.1696142094175
1977-01-01	41.6873635215074
1978-01-01	42.2162474080368
1979-01-01	42.7917048388440
1980-01-01	43.4368811293944
1981-01-01	43.8998068770434
1982-01-01	44.3683436855986
1983-01-01	44.8115179139060
1984-01-01	45.1799747511897
1985-01-01	45.4447926591062
1986-01-01	45.8316063131900
1987-01-01	46.0373223458246
1988-01-01	46.1164576046190
1989-01-01	46.1373568567151
1990-01-01	46.1309123957798
1991-01-01	46.1643630894129
1992-01-01	46.1689875799774
1993-01-01	46.1199060417852
1994-01-01	45.9752267765623
1995-01-01	45.7220069614342
1996-01-01	45.7700205338809
1997-01-01	45.6938766341704
1998-01-01	45.5373922319498
1999-01-01	45.3531881709772
2000-01-01	45.1624761005414
2001-01-01	44.8935394694488
2002-01-01	44.5978927317102
2003-01-01	44.2760456008998
2004-01-01	43.9314397431767
2005-01-01	43.5783922516617
2006-01-01	43.3327269162132
2007-01-01	43.0723437333588
2008-01-01	42.8119561789551
2009-01-01	42.5637649527364
2010-01-01	42.3336632645191
2011-01-01	42.2457356871580
2012-01-01	42.1276216487123
2013-01-01	41.9924531443745
2014-01-01	41.8486751221502
2015-01-01	41.6937113603528
2016-01-01	41.6147398961722
2017-01-01	41.4963226978380