Year	Percent of Total
1960-01-01	48.2005693916471
1961-01-01	48.5048435266546
1962-01-01	48.7515328241621
1963-01-01	48.9290743653927
1964-01-01	49.0138522111488
1965-01-01	48.9920462970888
1966-01-01	48.9037643310112
1967-01-01	48.7176702482286
1968-01-01	48.4512444044447
1969-01-01	48.1241090717802
1970-01-01	47.7456933135603
1971-01-01	47.3374656724063
1972-01-01	46.8875198689730
1973-01-01	46.4054340827858
1974-01-01	45.8972884205174
1975-01-01	45.3669803599463
1976-01-01	44.8389358805603
1977-01-01	44.2928269644568
1978-01-01	43.7443052848940
1979-01-01	43.2130869807966
1980-01-01	42.7093150618434
1981-01-01	42.2133521637004
1982-01-01	41.7667573640937
1983-01-01	41.3560923445222
1984-01-01	40.9587736705181
1985-01-01	40.5614333250730
1986-01-01	40.1800969495100
1987-01-01	39.7851233121013
1988-01-01	39.3925470020494
1989-01-01	39.0271132625494
1990-01-01	38.6967093455455
1991-01-01	38.3300148437907
1992-01-01	38.0149777379843
1993-01-01	37.7244328128685
1994-01-01	37.4167618119935
1995-01-01	37.0693005177244
1996-01-01	36.7094721421906
1997-01-01	36.2976316939655
1998-01-01	35.8580705428576
1999-01-01	35.4343019762936
2000-01-01	35.0482947863400
2001-01-01	34.6147336487939
2002-01-01	34.2524046721771
2003-01-01	33.9286622300329
2004-01-01	33.5961734804292
2005-01-01	33.2344472559114
2006-01-01	32.8956334730430
2007-01-01	32.5169424999261
2008-01-01	32.1236815779970
2009-01-01	31.7567654726909
2010-01-01	31.4327714176168
2011-01-01	31.0909191545508
2012-01-01	30.7958581775390
2013-01-01	30.5277564229257
2014-01-01	30.2543839788488
2015-01-01	29.9588427256807
2016-01-01	29.6353172862534
2017-01-01	29.2986215842150