Year	Percent of Total
1960-01-01	55.2262879152624
1961-01-01	54.4646226415094
1962-01-01	53.4926047090264
1963-01-01	52.5173552604974
1964-01-01	51.8762733028106
1965-01-01	51.6526981955016
1966-01-01	51.0114519769289
1967-01-01	50.6910087091630
1968-01-01	50.5781387533008
1969-01-01	50.4987482397121
1970-01-01	50.4153537668290
1971-01-01	50.8388105833504
1972-01-01	51.2688882036026
1973-01-01	51.7100660707345
1974-01-01	52.1971874623475
1975-01-01	52.7605302903172
1976-01-01	53.1501285599646
1977-01-01	53.6064000000000
1978-01-01	54.0874792573343
1979-01-01	54.5807560664897
1980-01-01	55.0894500256433
1981-01-01	55.7208237986270
1982-01-01	56.3270156084966
1983-01-01	56.8967769086767
1984-01-01	57.4396406513195
1985-01-01	57.9471905607423
1986-01-01	57.8281241071939
1987-01-01	57.7355957379953
1988-01-01	57.6468066866695
1989-01-01	57.5587363138686
1990-01-01	57.4719642048029
1991-01-01	58.4685314685315
1992-01-01	59.3863461326879
1993-01-01	60.2045497476860
1994-01-01	60.9609092474600
1995-01-01	61.6885910590198
1996-01-01	61.9774702285163
1997-01-01	62.3446640920736
1998-01-01	62.7860281860888
1999-01-01	63.2271926646763
2000-01-01	63.6196719695383
2001-01-01	64.7377281480494
2002-01-01	65.6769948814175
2003-01-01	66.4672331509719
2004-01-01	67.2122902473595
2005-01-01	67.9888217795006
2006-01-01	68.1671667094213
2007-01-01	68.4485107608467
2008-01-01	68.8088569349183
2009-01-01	69.1895335808599
2010-01-01	69.5290192002626
2011-01-01	69.8760807544047
2012-01-01	70.1424933629517
2013-01-01	70.2646472268636
2014-01-01	70.2350569412572
2015-01-01	70.0507776663609
2016-01-01	69.5844122766057
2017-01-01	69.1556625183403