Year	Percent of Total
1960-01-01	48.3260715938035
1961-01-01	48.2977040741141
1962-01-01	48.0958401430818
1963-01-01	47.7765194586069
1964-01-01	47.3875013875014
1965-01-01	46.9267035006672
1966-01-01	46.4603925059413
1967-01-01	45.9239659529465
1968-01-01	45.3067998685086
1969-01-01	44.5922559834242
1970-01-01	43.7827671464990
1971-01-01	43.1611302461809
1972-01-01	42.4639010784541
1973-01-01	41.7117993456138
1974-01-01	40.9375508500357
1975-01-01	40.1710039108907
1976-01-01	39.9845111655774
1977-01-01	39.7949717430076
1978-01-01	39.6041651281294
1979-01-01	39.4251035334927
1980-01-01	39.2746220021881
1981-01-01	39.1298937714589
1982-01-01	39.0078988563270
1983-01-01	38.9736661263425
1984-01-01	39.0197411067927
1985-01-01	39.0700066464230
1986-01-01	38.9929413205520
1987-01-01	38.8916831203021
1988-01-01	38.7572847228658
1989-01-01	38.5998807657489
1990-01-01	38.4385447718177
1991-01-01	38.1369540418207
1992-01-01	37.8384513203614
1993-01-01	37.4973841960409
1994-01-01	37.0715990110583
1995-01-01	36.5664385981653
1996-01-01	36.3711573075531
1997-01-01	36.0527709810055
1998-01-01	35.6834496417036
1999-01-01	35.3402505164329
2000-01-01	35.0262504884600
2001-01-01	33.9717372988561
2002-01-01	33.0516090038998
2003-01-01	32.2002184593230
2004-01-01	31.3564789809789
2005-01-01	30.5288160259523
2006-01-01	30.3597607476816
2007-01-01	30.0930029755202
2008-01-01	29.7506343823369
2009-01-01	29.3734381730748
2010-01-01	28.9973835688121
2011-01-01	28.9647163026505
2012-01-01	28.9030627429613
2013-01-01	28.8391126671706
2014-01-01	28.7883577216682
2015-01-01	28.7444137694488
2016-01-01	28.5931728158797
2017-01-01	28.4700641191295