Year	Percent of Total
1960-01-01	53.4018459789026
1961-01-01	52.9434426465094
1962-01-01	52.7945274476714
1963-01-01	52.8581549097228
1964-01-01	52.9894212704255
1965-01-01	53.1217915505864
1966-01-01	53.3834037003875
1967-01-01	53.5913802879629
1968-01-01	53.8148603001453
1969-01-01	54.1596411486332
1970-01-01	54.6653865400548
1971-01-01	55.2017082432339
1972-01-01	55.8344144564244
1973-01-01	56.5419810666872
1974-01-01	57.2922915780096
1975-01-01	58.0737878423547
1976-01-01	58.7917382357840
1977-01-01	59.6166531689892
1978-01-01	60.4789744255064
1979-01-01	61.2905307471886
1980-01-01	62.0122156851656
1981-01-01	62.8202617356140
1982-01-01	63.4754640463538
1983-01-01	64.0593092819626
1984-01-01	64.7060980857238
1985-01-01	65.4781180883848
1986-01-01	66.0948415456044
1987-01-01	66.9303657233234
1988-01-01	67.8676043677339
1989-01-01	68.7061038229537
1990-01-01	69.3370061937001
1991-01-01	70.0238929315970
1992-01-01	70.3694952333053
1993-01-01	70.5148500837540
1994-01-01	70.6890315718251
1995-01-01	70.9954793095091
1996-01-01	71.0404081214386
1997-01-01	71.3383492410947
1998-01-01	71.7500715565739
1999-01-01	72.0654824740111
2000-01-01	72.1995921522654
2001-01-01	72.3769694615205
2002-01-01	72.3731900398431
2003-01-01	72.2771992291064
2004-01-01	72.2340984075597
2005-01-01	72.3077844097715
2006-01-01	72.4428057230630
2007-01-01	72.6172750232158
2008-01-01	72.8265607265164
2009-01-01	73.0303167276397
2010-01-01	73.1933023838889
2011-01-01	73.2698640069078
2012-01-01	73.3358765624223
2013-01-01	73.3552482216096
2014-01-01	73.2917367595001
2015-01-01	73.1299307806579
2016-01-01	72.9130769798243
2017-01-01	72.6124966880605