Year	Percent of Total
1960-01-01	37.9922440680152
1961-01-01	37.8153077562889
1962-01-01	37.7319657837577
1963-01-01	37.6452874083169
1964-01-01	37.4289499796385
1965-01-01	37.0424608397721
1966-01-01	36.5859312125029
1967-01-01	36.0000924044177
1968-01-01	35.3281124899022
1969-01-01	34.6461399305005
1970-01-01	33.9948860994886
1971-01-01	33.4665692452118
1972-01-01	32.9073777348264
1973-01-01	32.3803047159060
1974-01-01	31.9391750046794
1975-01-01	31.5968297458139
1976-01-01	31.1228055952391
1977-01-01	30.7865887225166
1978-01-01	30.5166779571473
1979-01-01	30.2117128172894
1980-01-01	29.8244930222841
1981-01-01	29.4168516582283
1982-01-01	28.9595717770119
1983-01-01	28.4713069619690
1984-01-01	27.9997872787636
1985-01-01	27.5699533795534
1986-01-01	27.2764093063881
1987-01-01	26.9827343026110
1988-01-01	26.6997508911242
1989-01-01	26.4356217480357
1990-01-01	26.1908960299124
1991-01-01	25.9802578836524
1992-01-01	25.8011051668486
1993-01-01	25.6207069658291
1994-01-01	25.3960860936276
1995-01-01	25.1109793410015
1996-01-01	24.7264686648474
1997-01-01	24.2521625585930
1998-01-01	23.7214452672066
1999-01-01	23.1881738436293
2000-01-01	22.6795601967546
2001-01-01	22.1263807969486
2002-01-01	21.6408287650908
2003-01-01	21.1888327117705
2004-01-01	20.7176112164671
2005-01-01	20.2061184154325
2006-01-01	19.7715623477749
2007-01-01	19.2712221696108
2008-01-01	18.7503204542179
2009-01-01	18.2820201895227
2010-01-01	17.9055400028685
2011-01-01	17.5205548395253
2012-01-01	17.2640687046898
2013-01-01	17.1041253259682
2014-01-01	16.9751070399688
2015-01-01	16.8400256239095
2016-01-01	16.7850755763725
2017-01-01	16.6903166343440