Annual Percent of Total
1960-01-01 38.0801856767372
1961-01-01 38.4451695888259
1962-01-01 38.7031033682165
1963-01-01 38.8741667986660
1964-01-01 38.9904795200962
1965-01-01 39.0527415942288
1966-01-01 38.8681771195201
1967-01-01 38.5494102383136
1968-01-01 38.1257931104263
1969-01-01 37.6448533707700
1970-01-01 37.1206792604502
1971-01-01 35.9097631595392
1972-01-01 34.8354256319349
1973-01-01 33.8037501646253
1974-01-01 32.6978518763878
1975-01-01 31.5196273685751
1976-01-01 31.0607652640597
1977-01-01 30.4770403241366
1978-01-01 29.9789626927753
1979-01-01 29.7515297977124
1980-01-01 29.7746972568737
1981-01-01 28.9252410305042
1982-01-01 28.3543635582904
1983-01-01 27.9139392891662
1984-01-01 27.4180718123146
1985-01-01 26.8103030587206
1986-01-01 26.3469088869500
1987-01-01 25.7353140976123
1988-01-01 25.0689483110081
1989-01-01 24.4952940360290
1990-01-01 24.0776728859256
1991-01-01 23.6440532006506
1992-01-01 23.3713727763708
1993-01-01 23.2005138945376
1994-01-01 23.0418726208738
1995-01-01 22.8537245385135
1996-01-01 22.6793812184612
1997-01-01 22.4731686302422
1998-01-01 22.2616159731293
1999-01-01 22.0803801845888
2000-01-01 21.9416928852276
2001-01-01 21.5915178159115
2002-01-01 21.3302735396607
2003-01-01 21.1259173284164
2004-01-01 20.9300196637751
2005-01-01 20.7270564105559
2006-01-01 20.5472678420151
2007-01-01 20.3519826181423
2008-01-01 20.1616189298245
2009-01-01 20.0150824146228
2010-01-01 19.9203058994381
2011-01-01 19.7169646580019
2012-01-01 19.5869808405988
2013-01-01 19.5059272447957
2014-01-01 19.4392787197629
2015-01-01 19.3658366670537
2016-01-01 19.2090415304074
2017-01-01 19.0606854986893