Year	Percent of Total
1960-01-01	30.0563018869111
1961-01-01	29.9468345142621
1962-01-01	29.6089498472217
1963-01-01	29.1376409550315
1964-01-01	28.6945696575963
1965-01-01	28.3583805288290
1966-01-01	28.1396782523458
1967-01-01	27.9647210575846
1968-01-01	27.8210849052557
1969-01-01	27.6540884030635
1970-01-01	27.4260393235073
1971-01-01	27.1480564395983
1972-01-01	26.8087123613053
1973-01-01	26.4044147417554
1974-01-01	25.9374605067319
1975-01-01	25.4126437857676
1976-01-01	24.8442881989631
1977-01-01	24.2426266564466
1978-01-01	23.6128348991638
1979-01-01	22.9689991031797
1980-01-01	22.3265574271040
1981-01-01	21.6711569223981
1982-01-01	21.0569101539347
1983-01-01	20.4819223431882
1984-01-01	19.9449337025384
1985-01-01	19.4531894799961
1986-01-01	19.1224914367225
1987-01-01	18.8059865764005
1988-01-01	18.5319748060754
1989-01-01	18.3292369081131
1990-01-01	18.2052151061565
1991-01-01	18.1580971818616
1992-01-01	18.1723729254559
1993-01-01	18.2346928603513
1994-01-01	18.3105603964313
1995-01-01	18.3732568926349
1996-01-01	18.4352694857213
1997-01-01	18.4692958853053
1998-01-01	18.4759571962969
1999-01-01	18.4711676399952
2000-01-01	18.4678467942235
2001-01-01	18.4284928924841
2002-01-01	18.4199541226745
2003-01-01	18.4214185945010
2004-01-01	18.3957851026654
2005-01-01	18.3203583664311
2006-01-01	18.2508910159486
2007-01-01	18.0973457653503
2008-01-01	17.8945355752588
2009-01-01	17.6945215249048
2010-01-01	17.5222474582832
2011-01-01	17.3317061203673
2012-01-01	17.1854766442146
2013-01-01	17.0624843116258
2014-01-01	16.9244049329057
2015-01-01	16.7556109900883
2016-01-01	16.5913536735908
2017-01-01	16.4135429466813