Year	Percent of Total
1960-01-01	42.0316976659330
1961-01-01	42.1845068547692
1962-01-01	42.0995155806676
1963-01-01	41.8729570692011
1964-01-01	41.6429285254838
1965-01-01	41.4711216841805
1966-01-01	41.2187739523190
1967-01-01	41.0563011787957
1968-01-01	40.9114017871750
1969-01-01	40.6691200500894
1970-01-01	40.2798597057319
1971-01-01	39.9290562277129
1972-01-01	39.4152792492083
1973-01-01	38.8082948746111
1974-01-01	38.2228955058908
1975-01-01	37.7197620587647
1976-01-01	37.2408274510400
1977-01-01	36.8819356907092
1978-01-01	36.5878513017210
1979-01-01	36.2713810705768
1980-01-01	35.8946308078502
1981-01-01	35.6457056589463
1982-01-01	35.3130121144859
1983-01-01	34.9330525048894
1984-01-01	34.5584174251048
1985-01-01	34.2065190438742
1986-01-01	33.8245400165762
1987-01-01	33.4250623725631
1988-01-01	33.0073428274023
1989-01-01	32.5664687380356
1990-01-01	32.1019973037061
1991-01-01	31.5666182981138
1992-01-01	31.0779314181334
1993-01-01	30.5985929947811
1994-01-01	30.0805134258663
1995-01-01	29.5028130739090
1996-01-01	28.9973993202744
1997-01-01	28.4215223604248
1998-01-01	27.8086271487544
1999-01-01	27.2349292839619
2000-01-01	26.7530752151349
2001-01-01	26.3647742982175
2002-01-01	26.0857429181554
2003-01-01	25.8932787282556
2004-01-01	25.7376859965380
2005-01-01	25.5900543305513
2006-01-01	25.5967684233842
2007-01-01	25.5794405765464
2008-01-01	25.5394510492217
2009-01-01	25.4894250515291
2010-01-01	25.4308061652354
2011-01-01	25.3021004117299
2012-01-01	25.1566166313048
2013-01-01	24.9883264831651
2014-01-01	24.7943371960346
2015-01-01	24.5750756491732
2016-01-01	24.2861213207188
2017-01-01	24.0125062527192