Year	Percent of Total
1960-01-01	34.8314468428212
1961-01-01	34.8755741496162
1962-01-01	35.0267699666283
1963-01-01	35.1976324815542
1964-01-01	35.2382482165635
1965-01-01	35.0541574406066
1966-01-01	34.9438480037759
1967-01-01	34.6041050187749
1968-01-01	34.0697426282857
1969-01-01	33.4773848692108
1970-01-01	32.9475308641975
1971-01-01	32.2585149564066
1972-01-01	31.6900663252773
1973-01-01	31.1984201071858
1974-01-01	30.6778222162049
1975-01-01	30.0722402040912
1976-01-01	29.5967510255646
1977-01-01	29.0021166846741
1978-01-01	28.3531793367669
1979-01-01	27.7679798243325
1980-01-01	27.3108751726204
1981-01-01	26.8306088104722
1982-01-01	26.5107818205639
1983-01-01	26.2916544354832
1984-01-01	26.0664455861287
1985-01-01	25.7823900354388
1986-01-01	25.8131245365916
1987-01-01	25.7493146043188
1988-01-01	25.6271781810981
1989-01-01	25.5153177081386
1990-01-01	25.4395920663673
1991-01-01	24.9684526448620
1992-01-01	24.5860149196658
1993-01-01	24.2421451332467
1994-01-01	23.8649924848891
1995-01-01	23.4246809388570
1996-01-01	23.1199583028754
1997-01-01	22.7384926951098
1998-01-01	22.2998669565500
1999-01-01	21.8545513706988
2000-01-01	21.4454984027642
2001-01-01	21.1398051127329
2002-01-01	20.8615512030024
2003-01-01	20.6174268885860
2004-01-01	20.3935657446618
2005-01-01	20.1783616812787
2006-01-01	20.0295549599244
2007-01-01	19.8665340832047
2008-01-01	19.6794938868811
2009-01-01	19.4688304765819
2010-01-01	19.2452165277077
2011-01-01	19.1183853318965
2012-01-01	18.9648236071687
2013-01-01	18.7930358128128
2014-01-01	18.6201754413915
2015-01-01	18.4583032197880
2016-01-01	18.2647566475506
2017-01-01	18.1175273467311