Year	Percent of Total
1960-01-01	31.4632708304500
1961-01-01	31.3030215649032
1962-01-01	31.2044252983793
1963-01-01	31.0884235366809
1964-01-01	30.8431137487427
1965-01-01	30.4213437263600
1966-01-01	30.0166017647438
1967-01-01	29.4436614177653
1968-01-01	28.7591158374776
1969-01-01	28.0852176255732
1970-01-01	27.5065374618763
1971-01-01	26.9930061065709
1972-01-01	26.6160524507938
1973-01-01	26.3511315052969
1974-01-01	26.1420455632281
1975-01-01	25.9650839340647
1976-01-01	25.9848459131802
1977-01-01	25.9848486253572
1978-01-01	25.9990920219073
1979-01-01	26.0598595901117
1980-01-01	26.1628052420673
1981-01-01	26.2617519838343
1982-01-01	26.3669689331066
1983-01-01	26.4626965125635
1984-01-01	26.5229378601452
1985-01-01	26.5289837148656
1986-01-01	26.3829085155938
1987-01-01	26.2350528040546
1988-01-01	26.0427273954641
1989-01-01	25.7642395653987
1990-01-01	25.3891780093010
1991-01-01	25.0184442768120
1992-01-01	24.5373222496464
1993-01-01	23.9762425816509
1994-01-01	23.3842125597811
1995-01-01	22.7857843128136
1996-01-01	22.2072995259981
1997-01-01	21.5965116512007
1998-01-01	20.9678358053207
1999-01-01	20.3358721887142
2000-01-01	19.7134173863552
2001-01-01	19.0327010747766
2002-01-01	18.4223449923836
2003-01-01	17.8630808131875
2004-01-01	17.3304757419270
2005-01-01	16.8224342341298
2006-01-01	16.4328102722569
2007-01-01	16.0746868566293
2008-01-01	15.7626912071743
2009-01-01	15.5146379583904
2010-01-01	15.3351020503326
2011-01-01	15.2667533850772
2012-01-01	15.2143871133288
2013-01-01	15.1950828828065
2014-01-01	15.2197901613539
2015-01-01	15.2835704770341
2016-01-01	15.2987260980365
2017-01-01	15.3687765503807