Year	Percent of Total
1960-01-01	33.5546129355715
1961-01-01	33.5694580465697
1962-01-01	33.2602027309961
1963-01-01	32.7015716141770
1964-01-01	32.0416701079957
1965-01-01	31.3664166846792
1966-01-01	30.4770950009555
1967-01-01	29.6851294792409
1968-01-01	28.9275815936849
1969-01-01	28.1145589382451
1970-01-01	27.2284030574382
1971-01-01	26.5216229736881
1972-01-01	25.7482148593616
1973-01-01	24.9838696975082
1974-01-01	24.3462952604558
1975-01-01	23.8959056568911
1976-01-01	23.6998124970777
1977-01-01	23.6314058185268
1978-01-01	23.6872279709117
1979-01-01	23.8295308613360
1980-01-01	24.0264641942273
1981-01-01	24.3225523433846
1982-01-01	24.6709357274842
1983-01-01	25.0324411095710
1984-01-01	25.3467310943532
1985-01-01	25.5672637435869
1986-01-01	25.6830699252147
1987-01-01	25.6647684173582
1988-01-01	25.5341035236300
1989-01-01	25.3424073766534
1990-01-01	25.1199954851267
1991-01-01	24.7498182180508
1992-01-01	24.4106368761003
1993-01-01	24.0536832107105
1994-01-01	23.6081681521828
1995-01-01	23.0460453266242
1996-01-01	22.4894566371405
1997-01-01	21.7943533686761
1998-01-01	21.0186203899191
1999-01-01	20.2563040928648
2000-01-01	19.5573234533046
2001-01-01	18.8342281650104
2002-01-01	18.1956946167795
2003-01-01	17.6268546807335
2004-01-01	17.0991944851850
2005-01-01	16.6105348361347
2006-01-01	16.1899720184921
2007-01-01	15.8604352225572
2008-01-01	15.6066313641485
2009-01-01	15.3996060521536
2010-01-01	15.2172555035693
2011-01-01	15.1785366890855
2012-01-01	15.0772166089331
2013-01-01	14.9597053740081
2014-01-01	14.8885568298799
2015-01-01	14.8838164447271
2016-01-01	14.8043985505597
2017-01-01	14.8175517396689