Year	Percent of Total
1960-01-01	26.2655663106016
1961-01-01	26.3873263792353
1962-01-01	26.2715851585168
1963-01-01	25.9957713254207
1964-01-01	25.7035739454694
1965-01-01	25.4623612334100
1966-01-01	25.3174253133190
1967-01-01	25.1637037202912
1968-01-01	25.0170511413347
1969-01-01	24.8804382575858
1970-01-01	24.7538654100973
1971-01-01	24.5574660735854
1972-01-01	24.4063524977862
1973-01-01	24.2661146947059
1974-01-01	24.0765838399195
1975-01-01	23.8053937382111
1976-01-01	23.5679830701828
1977-01-01	23.2224877346983
1978-01-01	22.8161793107638
1979-01-01	22.4350671746023
1980-01-01	22.1266362592598
1981-01-01	21.7840402909534
1982-01-01	21.5706227549003
1983-01-01	21.4216114931360
1984-01-01	21.2395415596643
1985-01-01	20.9856108622410
1986-01-01	20.8546818502651
1987-01-01	20.6074170254204
1988-01-01	20.3094653541282
1989-01-01	20.0558443535950
1990-01-01	19.8841098449487
1991-01-01	19.7192175884350
1992-01-01	19.6307861349364
1993-01-01	19.5878504773242
1994-01-01	19.5362370503071
1995-01-01	19.4511171540037
1996-01-01	19.3161437148837
1997-01-01	19.1830458400166
1998-01-01	19.0465707576707
1999-01-01	18.9105633651919
2000-01-01	18.7806942873515
2001-01-01	18.7007726027825
2002-01-01	18.6099291929495
2003-01-01	18.5226491049222
2004-01-01	18.4565433248727
2005-01-01	18.4173913469500
2006-01-01	18.3974953989815
2007-01-01	18.3977860249076
2008-01-01	18.4105594701147
2009-01-01	18.4185637202020
2010-01-01	18.4097083238003
2011-01-01	18.4117483608480
2012-01-01	18.3981715362631
2013-01-01	18.3659108944087
2014-01-01	18.3201855697399
2015-01-01	18.2651337900943
2016-01-01	18.1742778082249
2017-01-01	18.0836145551520