Year	Percent of Total
1960-01-01	39.8991555181796
1961-01-01	40.1482444888089
1962-01-01	40.4784237414393
1963-01-01	40.8033178657122
1964-01-01	41.0142008849023
1965-01-01	41.0744007060649
1966-01-01	41.2255915281891
1967-01-01	41.1935415214881
1968-01-01	41.0476444405174
1969-01-01	40.8824493467321
1970-01-01	40.7387692741634
1971-01-01	40.6855435066115
1972-01-01	40.6081710047601
1973-01-01	40.5029106213468
1974-01-01	40.3423108308778
1975-01-01	40.1102904026543
1976-01-01	39.8804364247040
1977-01-01	39.5818383209954
1978-01-01	39.2288236175736
1979-01-01	38.8475362145155
1980-01-01	38.4590834712060
1981-01-01	38.0956210105164
1982-01-01	37.7502444118298
1983-01-01	37.4160607809310
1984-01-01	37.0856806895008
1985-01-01	36.7615501786376
1986-01-01	36.5785248706230
1987-01-01	36.3803758332399
1988-01-01	36.1751612417367
1989-01-01	35.9596747551292
1990-01-01	35.7285531027496
1991-01-01	35.5961918338723
1992-01-01	35.3692720106953
1993-01-01	35.0821925159556
1994-01-01	34.7770067733033
1995-01-01	34.4684468316697
1996-01-01	34.0597125450021
1997-01-01	33.7042139447077
1998-01-01	33.3530014171639
1999-01-01	32.9443204153521
2000-01-01	32.4609404114365
2001-01-01	32.0370839106993
2002-01-01	31.5471819708289
2003-01-01	31.0246487195712
2004-01-01	30.5297715829723
2005-01-01	30.0944588353929
2006-01-01	29.7545237929405
2007-01-01	29.4507336062768
2008-01-01	29.1856859402149
2009-01-01	28.9510787293923
2010-01-01	28.7412495400983
2011-01-01	28.5724373431975
2012-01-01	28.4249987414366
2013-01-01	28.2909883511929
2014-01-01	28.1571542679788
2015-01-01	28.0138775452618
2016-01-01	27.8844187145896
2017-01-01	27.7367339500670