Year	Percent of Total
1960-01-01	29.0221393203558
1961-01-01	29.0245900625881
1962-01-01	28.9136554567714
1963-01-01	28.7221414664080
1964-01-01	28.5056913086996
1965-01-01	28.2915033453888
1966-01-01	28.1213369247961
1967-01-01	27.9325606775746
1968-01-01	27.7298786702011
1969-01-01	27.5035143035043
1970-01-01	27.2683260900310
1971-01-01	26.9651874286178
1972-01-01	26.6729513046330
1973-01-01	26.3804268143692
1974-01-01	26.0599946580678
1975-01-01	25.7051731374629
1976-01-01	25.3988394694847
1977-01-01	25.0385858193200
1978-01-01	24.6470338550264
1979-01-01	24.2627005840454
1980-01-01	23.9067492913385
1981-01-01	23.5701196923905
1982-01-01	23.2761478503263
1983-01-01	23.0108504149589
1984-01-01	22.7475844422668
1985-01-01	22.4738336384086
1986-01-01	22.2595533915517
1987-01-01	22.0224771576269
1988-01-01	21.7764847853003
1989-01-01	21.5434876413842
1990-01-01	21.3355972868319
1991-01-01	21.1702033522863
1992-01-01	21.0063520933634
1993-01-01	20.8747695891490
1994-01-01	20.7269960562670
1995-01-01	20.5659158166208
1996-01-01	20.4026023339276
1997-01-01	20.2030996575690
1998-01-01	19.9846594252220
1999-01-01	19.7721955777133
2000-01-01	19.5758050538156
2001-01-01	19.3351554328244
2002-01-01	19.1207003595593
2003-01-01	18.9200190458153
2004-01-01	18.7171466627535
2005-01-01	18.5068623896800
2006-01-01	18.3380992000839
2007-01-01	18.1621182756219
2008-01-01	17.9881408232612
2009-01-01	17.8246813466628
2010-01-01	17.6701541698742
2011-01-01	17.5593494523184
2012-01-01	17.4245766136036
2013-01-01	17.2877178764689
2014-01-01	17.1681621799724
2015-01-01	17.0722976041828
2016-01-01	16.9700996284889
2017-01-01	16.9083709312258