Year	Percent of Total
1960-01-01	46.4384660178843
1961-01-01	47.0364019790369
1962-01-01	47.5327652007678
1963-01-01	47.9254238292708
1964-01-01	48.2130359297129
1965-01-01	48.4041216227377
1966-01-01	48.6971798113698
1967-01-01	48.8647872210937
1968-01-01	48.9496007758341
1969-01-01	49.0045010377526
1970-01-01	49.0584396771844
1971-01-01	49.2243200394183
1972-01-01	49.3700172504144
1973-01-01	49.4946867688461
1974-01-01	49.5871505459279
1975-01-01	49.6438361283609
1976-01-01	49.8014318228063
1977-01-01	49.8899354521553
1978-01-01	49.9321620097442
1979-01-01	49.9546698136457
1980-01-01	49.9692236580144
1981-01-01	50.0459688112606
1982-01-01	50.0955953581637
1983-01-01	50.1094279177105
1984-01-01	50.0694855953758
1985-01-01	49.9664880942537
1986-01-01	49.9247986591441
1987-01-01	49.8037294575516
1988-01-01	49.6098016765424
1989-01-01	49.3427567913821
1990-01-01	48.9998357868240
1991-01-01	48.6658876628139
1992-01-01	48.2231079348691
1993-01-01	47.7106376091991
1994-01-01	47.1856737894583
1995-01-01	46.6828571863206
1996-01-01	46.3108788792732
1997-01-01	46.0265266621524
1998-01-01	45.7749989141682
1999-01-01	45.4820243018416
2000-01-01	45.1230431023905
2001-01-01	44.9613479975949
2002-01-01	44.6695037627045
2003-01-01	44.3255035063291
2004-01-01	44.0339597531924
2005-01-01	43.8366532136006
2006-01-01	43.6681776042081
2007-01-01	43.5876743810946
2008-01-01	43.5410311364833
2009-01-01	43.4396783633376
2010-01-01	43.2406971563248
2011-01-01	42.9954485434890
2012-01-01	42.6391348573563
2013-01-01	42.2101629315949
2014-01-01	41.7690869487281
2015-01-01	41.3448744956708
2016-01-01	40.8852875104100
2017-01-01	40.4663960636349