Annual 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