Year	Percent of Total
1960-01-01	44.7216887715297
1961-01-01	44.9541470290907
1962-01-01	44.9418359120052
1963-01-01	44.7930293497518
1964-01-01	44.6435065818023
1965-01-01	44.5392958447328
1966-01-01	44.4967257058579
1967-01-01	44.4306105469372
1968-01-01	44.3126530953380
1969-01-01	44.0764139239542
1970-01-01	43.6852643728642
1971-01-01	43.1645209549295
1972-01-01	42.5226804886166
1973-01-01	41.7848390298751
1974-01-01	41.0092003246023
1975-01-01	40.2446926133078
1976-01-01	39.4477891440239
1977-01-01	38.7500254787168
1978-01-01	38.1195187970456
1979-01-01	37.5127218589043
1980-01-01	36.9217472826883
1981-01-01	36.5721198844886
1982-01-01	36.1680776528974
1983-01-01	35.7773376114412
1984-01-01	35.4808910959211
1985-01-01	35.3022251214457
1986-01-01	35.2089942613066
1987-01-01	35.1938976628110
1988-01-01	35.2172839581642
1989-01-01	35.2098656654372
1990-01-01	35.1323241801101
1991-01-01	34.9586179077096
1992-01-01	34.7101704208118
1993-01-01	34.3878666412851
1994-01-01	34.0038065324066
1995-01-01	33.5679248152767
1996-01-01	33.1089166498922
1997-01-01	32.6000176499739
1998-01-01	32.0387176953278
1999-01-01	31.4194604288227
2000-01-01	30.7432562388500
2001-01-01	30.1390513105741
2002-01-01	29.4682718367082
2003-01-01	28.7599209979905
2004-01-01	28.0602421090996
2005-01-01	27.3977533528209
2006-01-01	26.7453259543158
2007-01-01	26.1747823362518
2008-01-01	25.6532102436659
2009-01-01	25.1285185382407
2010-01-01	24.5790138341312
2011-01-01	24.1492724445351
2012-01-01	23.6614123995890
2013-01-01	23.1573765176406
2014-01-01	22.6981603022548
2015-01-01	22.3086317964862
2016-01-01	21.9414016998012
2017-01-01	21.6472483722735