Year	Percent of Total
1960-01-01	27.5099376668700
1961-01-01	27.3408514667370
1962-01-01	27.0542249285592
1963-01-01	26.6611716877874
1964-01-01	26.2132792069475
1965-01-01	25.7416168466962
1966-01-01	25.3032938901304
1967-01-01	24.7916884015397
1968-01-01	24.2447577301268
1969-01-01	23.7204270768870
1970-01-01	23.2578398000304
1971-01-01	22.8427683610983
1972-01-01	22.5415341355958
1973-01-01	22.3185044828460
1974-01-01	22.1088272303776
1975-01-01	21.8809273328571
1976-01-01	21.7413687741819
1977-01-01	21.5372212588604
1978-01-01	21.3155537798930
1979-01-01	21.1456517031236
1980-01-01	21.0548899345799
1981-01-01	20.9414684104601
1982-01-01	20.9157291289278
1983-01-01	20.9301498860826
1984-01-01	20.9083291093445
1985-01-01	20.8119094585652
1986-01-01	20.7237773137702
1987-01-01	20.5533199766044
1988-01-01	20.3208507980107
1989-01-01	20.0621508173924
1990-01-01	19.7892040234722
1991-01-01	19.5273616424191
1992-01-01	19.2611785427084
1993-01-01	18.9848718530038
1994-01-01	18.7067419353592
1995-01-01	18.4427487397555
1996-01-01	18.1143271954040
1997-01-01	17.8876572870129
1998-01-01	17.7223145117592
1999-01-01	17.5475318489025
2000-01-01	17.3219405646521
2001-01-01	17.1234641839531
2002-01-01	16.7566044006816
2003-01-01	16.3157168030776
2004-01-01	15.9486258873337
2005-01-01	15.7308824439700
2006-01-01	15.4471859077919
2007-01-01	15.3964705499390
2008-01-01	15.4759136739310
2009-01-01	15.5177600802012
2010-01-01	15.4426380028617
2011-01-01	15.4704522286629
2012-01-01	15.3326664379548
2013-01-01	15.1038406136230
2014-01-01	14.9156095795382
2015-01-01	14.8279657111777
2016-01-01	14.7018523639031
2017-01-01	14.6886404654848