Year	Percent of Total
1960-01-01	31.7860911005910
1961-01-01	32.4017969246294
1962-01-01	33.0766002765812
1963-01-01	33.7048355371916
1964-01-01	34.1321531621389
1965-01-01	34.2823291904890
1966-01-01	34.1789194551434
1967-01-01	33.8460600606703
1968-01-01	33.3241872922292
1969-01-01	32.7204639796786
1970-01-01	32.1114263442275
1971-01-01	31.2749793033528
1972-01-01	30.6003377735078
1973-01-01	30.0387654295294
1974-01-01	29.4832799520926
1975-01-01	28.8721538144942
1976-01-01	28.4927031501849
1977-01-01	27.9596404070532
1978-01-01	27.3835023616614
1979-01-01	26.9436755159006
1980-01-01	26.7303068103998
1981-01-01	26.6236346880923
1982-01-01	26.7120162665874
1983-01-01	26.9092203503688
1984-01-01	27.0924519190231
1985-01-01	27.2129266633072
1986-01-01	27.4488527955064
1987-01-01	27.6689981581218
1988-01-01	27.8314917926214
1989-01-01	27.9180057854071
1990-01-01	27.9149316837591
1991-01-01	27.8960384380935
1992-01-01	27.7206682127656
1993-01-01	27.4170534063491
1994-01-01	27.0348747143576
1995-01-01	26.6012718819326
1996-01-01	26.0206966880664
1997-01-01	25.4704218107596
1998-01-01	24.9013938406182
1999-01-01	24.2385139407420
2000-01-01	23.4551327048772
2001-01-01	22.5152998264248
2002-01-01	21.4767170359928
2003-01-01	20.4000051778123
2004-01-01	19.3902461562759
2005-01-01	18.5156741745855
2006-01-01	17.9171381489265
2007-01-01	17.4271293103386
2008-01-01	17.0471902788317
2009-01-01	16.7503002900362
2010-01-01	16.5160273728780
2011-01-01	16.2470740928952
2012-01-01	16.0365642757953
2013-01-01	15.8836620363048
2014-01-01	15.7838974982180
2015-01-01	15.7269588143572
2016-01-01	15.7173549761455
2017-01-01	15.7399069710496