Year	Percent of Total
1960-01-01	6.16704929905440
1961-01-01	6.14922268975042
1962-01-01	6.11010509835927
1963-01-01	6.06110071939683
1964-01-01	6.01823593329239
1965-01-01	5.99234939510766
1966-01-01	6.15555488960645
1967-01-01	6.35536720926241
1968-01-01	6.59853213526305
1969-01-01	6.88086169708075
1970-01-01	7.19843908746652
1971-01-01	7.36419873523775
1972-01-01	7.51195177717730
1973-01-01	7.63968178995013
1974-01-01	7.74936239191765
1975-01-01	7.84069627721186
1976-01-01	7.94382100663249
1977-01-01	8.03968827972068
1978-01-01	8.11481678992941
1979-01-01	8.14679537351074
1980-01-01	8.12857078900877
1981-01-01	8.07419595805250
1982-01-01	7.97374335269436
1983-01-01	7.85449286611042
1984-01-01	7.75838446025883
1985-01-01	7.70973394830102
1986-01-01	7.74826926602602
1987-01-01	7.82186035275788
1988-01-01	7.92805164490717
1989-01-01	8.06888132860210
1990-01-01	8.24403823076998
1991-01-01	8.49107010902311
1992-01-01	8.77000252765842
1993-01-01	9.08068488103779
1994-01-01	9.42259435818373
1995-01-01	9.79652296692209
1996-01-01	10.13624180459480
1997-01-01	10.48824359123670
1998-01-01	10.84709738131550
1999-01-01	11.20800455543810
2000-01-01	11.56740987026530
2001-01-01	11.92677457495820
2002-01-01	12.28321013658700
2003-01-01	12.61494519595440
2004-01-01	12.88297880987410
2005-01-01	13.06384939356380
2006-01-01	13.10615183415560
2007-01-01	13.07362256329460
2008-01-01	13.00826619231980
2009-01-01	12.96327217380690
2010-01-01	12.96699424141220
2011-01-01	13.06162125519210
2012-01-01	13.18867279920050
2013-01-01	13.36051692409750
2014-01-01	13.59272488584840
2015-01-01	13.89367344924530
2016-01-01	14.29825887069190
2017-01-01	14.76214703637750