Year	Percent of Total
1960-01-01	54.0396536707823
1961-01-01	53.8815161765981
1962-01-01	53.2545934896176
1963-01-01	52.3993228692838
1964-01-01	51.6786490924422
1965-01-01	51.2864145208587
1966-01-01	51.2787908861597
1967-01-01	51.3721020903938
1968-01-01	51.4740874006152
1969-01-01	51.5239993636355
1970-01-01	51.5706593058509
1971-01-01	51.7981331956995
1972-01-01	52.3161338868269
1973-01-01	52.9610317434372
1974-01-01	53.5814240311181
1975-01-01	54.1100452460974
1976-01-01	54.7444117908986
1977-01-01	55.1978914621500
1978-01-01	55.5875608255495
1979-01-01	56.0904573104497
1980-01-01	56.7827668942969
1981-01-01	57.3299283807914
1982-01-01	58.1155835115111
1983-01-01	59.0642038970371
1984-01-01	59.9867367778586
1985-01-01	60.7280655692792
1986-01-01	61.0340136054422
1987-01-01	61.1262503379292
1988-01-01	61.0578798132161
1989-01-01	60.9924222144431
1990-01-01	61.0399495904222
1991-01-01	61.0139790907651
1992-01-01	61.2108191322479
1993-01-01	61.5330341500876
1994-01-01	61.8497109826590
1995-01-01	62.1061729771929
1996-01-01	62.5465722377020
1997-01-01	62.8075680169489
1998-01-01	63.0328931236207
1999-01-01	63.3954634431128
2000-01-01	63.9531649090863
2001-01-01	64.4850439129119
2002-01-01	65.2102397492306
2003-01-01	66.0063018362247
2004-01-01	66.7032072286764
2005-01-01	67.2245631380303
2006-01-01	67.5874212665612
2007-01-01	67.8549774745389
2008-01-01	68.0776201748620
2009-01-01	68.2996901133741
2010-01-01	68.5191546561123
2011-01-01	68.6929066160693
2012-01-01	68.7780407282952
2013-01-01	68.8112368752011
2014-01-01	68.8283167080484
2015-01-01	68.8407936908063
2016-01-01	68.8806172557529
2017-01-01	68.9399908836177