Year	Percent of Total
1960-01-01	34.5585235407132
1961-01-01	35.4872965725967
1962-01-01	36.3728805543075
1963-01-01	37.2793775056529
1964-01-01	38.1193928063306
1965-01-01	38.8682177745305
1966-01-01	40.1921669943756
1967-01-01	41.2615046104797
1968-01-01	42.2451200745948
1969-01-01	43.1959880138151
1970-01-01	44.0500182787938
1971-01-01	44.3885104014020
1972-01-01	44.7670500021062
1973-01-01	45.1192048606525
1974-01-01	45.3042699573191
1975-01-01	45.2414775499054
1976-01-01	44.4309586130853
1977-01-01	43.3950457765682
1978-01-01	42.2568896571443
1979-01-01	41.2010467167763
1980-01-01	40.3343102691942
1981-01-01	39.4633784964702
1982-01-01	38.8770301869764
1983-01-01	38.4969866598171
1984-01-01	38.1171289616767
1985-01-01	37.6108830737771
1986-01-01	37.4954591376855
1987-01-01	37.0469062852260
1988-01-01	36.4072029565179
1989-01-01	35.6956734886968
1990-01-01	34.8868721170310
1991-01-01	33.6778569712737
1992-01-01	32.6226982743285
1993-01-01	31.7301367311580
1994-01-01	31.0379270306719
1995-01-01	30.7145371654070
1996-01-01	30.1193204799784
1997-01-01	29.5733609123461
1998-01-01	29.1593174079276
1999-01-01	28.8110876178933
2000-01-01	28.3944681459043
2001-01-01	27.9880342569174
2002-01-01	27.4333401902107
2003-01-01	26.8157841113300
2004-01-01	26.2942046859084
2005-01-01	25.9773796539875
2006-01-01	25.1537695950545
2007-01-01	24.5295417051142
2008-01-01	24.0788888302405
2009-01-01	23.6670960244262
2010-01-01	23.2107316575292
2011-01-01	22.8144583085635
2012-01-01	22.3075690696899
2013-01-01	21.7610956026106
2014-01-01	21.2771880659361
2015-01-01	20.8859000242391
2016-01-01	20.9783683694157
2017-01-01	21.0913597103658