Year	Percent of Total
1960-01-01	25.3281741246915
1961-01-01	24.9165946199442
1962-01-01	24.5777423196605
1963-01-01	24.2530027803145
1964-01-01	23.8611651585363
1965-01-01	23.3845047719596
1966-01-01	22.8179487119205
1967-01-01	22.2965773754349
1968-01-01	21.7967388157544
1969-01-01	21.3030474207263
1970-01-01	20.8217557980927
1971-01-01	20.6641533414333
1972-01-01	20.4007682018747
1973-01-01	20.1399264974565
1974-01-01	20.0340643146314
1975-01-01	20.1492884670005
1976-01-01	20.3121873067121
1977-01-01	20.7386092019863
1978-01-01	21.3005650268019
1979-01-01	21.7695454047131
1980-01-01	22.0142214158820
1981-01-01	22.3178864577835
1982-01-01	22.2849645083519
1983-01-01	22.0357605415639
1984-01-01	21.7930153546612
1985-01-01	21.6718998729703
1986-01-01	21.2117717983997
1987-01-01	21.0387509663446
1988-01-01	20.9887411144387
1989-01-01	20.8130434105490
1990-01-01	20.4133189678473
1991-01-01	20.1815610923038
1992-01-01	19.6811743983069
1993-01-01	19.0452922408408
1994-01-01	18.4844028676241
1995-01-01	18.0868628088671
1996-01-01	17.7365039293084
1997-01-01	17.4668945317994
1998-01-01	17.2592215382176
1999-01-01	17.0548487071997
2000-01-01	16.8292673620355
2001-01-01	16.4895053514296
2002-01-01	16.2286759707439
2003-01-01	16.0052163507710
2004-01-01	15.7732992943902
2005-01-01	15.5175276967699
2006-01-01	15.4620418248119
2007-01-01	15.3345603357261
2008-01-01	15.1578774163386
2009-01-01	14.9885801122248
2010-01-01	14.8603220841593
2011-01-01	14.7196097393022
2012-01-01	14.6123421985952
2013-01-01	14.5385191192129
2014-01-01	14.4846578660568
2015-01-01	14.4410653188776
2016-01-01	14.3546874123692
2017-01-01	14.3169732344370