Year	Percent of Total
1960-01-01	38.9414959522877
1961-01-01	38.1692733466703
1962-01-01	37.0870260798903
1963-01-01	35.7555749463690
1964-01-01	34.3473472095323
1965-01-01	32.9693881047539
1966-01-01	31.9120290044340
1967-01-01	30.7575550219590
1968-01-01	29.5863592322239
1969-01-01	28.5181047020417
1970-01-01	27.6275750891948
1971-01-01	26.7181749448572
1972-01-01	26.2059147656852
1973-01-01	25.9348488720727
1974-01-01	25.6805612979237
1975-01-01	25.3385002834388
1976-01-01	25.1067753385202
1977-01-01	24.6943225414700
1978-01-01	24.2238750034278
1979-01-01	23.8869850065485
1980-01-01	23.7573288045272
1981-01-01	23.7497508871392
1982-01-01	23.8502749438619
1983-01-01	24.0073782644734
1984-01-01	24.1359973175159
1985-01-01	24.1944352168982
1986-01-01	24.1150492711503
1987-01-01	24.0036917501203
1988-01-01	23.8499573076472
1989-01-01	23.6481718740056
1990-01-01	23.4003144628201
1991-01-01	23.1530658888574
1992-01-01	22.8446857075021
1993-01-01	22.4977527127967
1994-01-01	22.1442099064736
1995-01-01	21.8038153587252
1996-01-01	21.4112220166271
1997-01-01	21.0491652547626
1998-01-01	20.6999398369197
1999-01-01	20.3273193585658
2000-01-01	19.9093448425383
2001-01-01	19.5763550500432
2002-01-01	19.1548530661371
2003-01-01	18.6728536671867
2004-01-01	18.1865992439637
2005-01-01	17.7350800295978
2006-01-01	17.0730095480991
2007-01-01	16.5086614480264
2008-01-01	16.0234199083780
2009-01-01	15.5777753625814
2010-01-01	15.1575304606955
2011-01-01	14.9701099752132
2012-01-01	14.7798540361084
2013-01-01	14.6106519612707
2014-01-01	14.4878633362314
2015-01-01	14.4133989373644
2016-01-01	14.4081218179531
2017-01-01	14.4277971845370