Annual 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