Year	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