Year	Percent of Total
1960-01-01	42.5949807408413
1961-01-01	42.6422616890178
1962-01-01	42.7549094863430
1963-01-01	42.9259851318424
1964-01-01	43.1233149071410
1965-01-01	43.2877593224550
1966-01-01	43.3246351736559
1967-01-01	43.3103315422667
1968-01-01	43.2521127793971
1969-01-01	43.2071025020178
1970-01-01	43.2522303325223
1971-01-01	43.9986282578875
1972-01-01	44.8701607202865
1973-01-01	45.7995305242851
1974-01-01	46.6742159156774
1975-01-01	47.4083072708005
1976-01-01	47.5603070175439
1977-01-01	47.5490172504172
1978-01-01	47.4601457183058
1979-01-01	47.3976769539294
1980-01-01	47.3988213714241
1981-01-01	47.5085856616306
1982-01-01	47.6467891583128
1983-01-01	47.7533032726359
1984-01-01	47.7448431534512
1985-01-01	47.5821728871016
1986-01-01	47.3120593319419
1987-01-01	46.9502863736348
1988-01-01	46.4999118536499
1989-01-01	45.9899819622559
1990-01-01	45.4540790148794
1991-01-01	45.0717530311486
1992-01-01	44.6315081238843
1993-01-01	44.1683163650075
1994-01-01	43.7239601975804
1995-01-01	43.3168626905143
1996-01-01	43.0225539896446
1997-01-01	42.7367501256754
1998-01-01	42.4638352664709
1999-01-01	42.1977496525858
2000-01-01	41.9346160650883
2001-01-01	41.7934991612658
2002-01-01	41.6808726697943
2003-01-01	41.5818913129604
2004-01-01	41.4704444890514
2005-01-01	41.3277716888175
2006-01-01	41.2126990457437
2007-01-01	41.0997281616424
2008-01-01	40.9919580079964
2009-01-01	40.8871509981999
2010-01-01	40.7667822429375
2011-01-01	40.6353430415074
2012-01-01	40.4247449372746
2013-01-01	40.1582572185558
2014-01-01	39.8633198031638
2015-01-01	39.5508287913502
2016-01-01	39.1992913137555
2017-01-01	38.8423520020676