Year	Percent of Total
1960-01-01	39.8691847476975
1961-01-01	40.4180512298693
1962-01-01	40.9196795025995
1963-01-01	41.3823847321462
1964-01-01	41.8013753636915
1965-01-01	42.1661592640031
1966-01-01	42.5248590353838
1967-01-01	42.8348875668304
1968-01-01	43.0713328104713
1969-01-01	43.2032081261902
1970-01-01	43.2217913423094
1971-01-01	43.2764029320467
1972-01-01	43.2006917126785
1973-01-01	43.0272949394416
1974-01-01	42.8007202999538
1975-01-01	42.5446475579506
1976-01-01	42.3283881308275
1977-01-01	42.0730555583187
1978-01-01	41.7807531061411
1979-01-01	41.4486697922921
1980-01-01	41.0789009844813
1981-01-01	40.7429802745868
1982-01-01	40.3726729139430
1983-01-01	39.9685371845293
1984-01-01	39.5259085537143
1985-01-01	39.0416172632476
1986-01-01	38.6051028780681
1987-01-01	38.1025835037439
1988-01-01	37.5555862804741
1989-01-01	36.9940973350406
1990-01-01	36.4338107533310
1991-01-01	35.8725286720712
1992-01-01	35.3407728805723
1993-01-01	34.8155323083032
1994-01-01	34.2606165722875
1995-01-01	33.6600710947041
1996-01-01	33.0973343343396
1997-01-01	32.4801603183293
1998-01-01	31.8374385943339
1999-01-01	31.2249081498239
2000-01-01	30.6862231048988
2001-01-01	30.4647436747628
2002-01-01	30.3114948030500
2003-01-01	30.2080592871084
2004-01-01	30.1264225314684
2005-01-01	30.0495636041258
2006-01-01	29.7394760336665
2007-01-01	29.4691747028674
2008-01-01	29.2468194219904
2009-01-01	29.0827529808811
2010-01-01	28.9676598480061
2011-01-01	28.6970759310650
2012-01-01	28.5034260564408
2013-01-01	28.3324952726390
2014-01-01	28.1247282279751
2015-01-01	27.8587086866615
2016-01-01	27.6525748824306
2017-01-01	27.3563459812830