Year	Percent of Total
1960-01-01	55.4341630678976
1961-01-01	55.2150186372494
1962-01-01	54.4933083127764
1963-01-01	53.5664224505426
1964-01-01	52.8388678977208
1965-01-01	52.4522155693198
1966-01-01	51.9261454296786
1967-01-01	51.7124520140144
1968-01-01	51.6675337734305
1969-01-01	51.5838693470273
1970-01-01	51.3777650153262
1971-01-01	50.9282702849276
1972-01-01	50.5298426533596
1973-01-01	50.1579740458687
1974-01-01	49.8194753412324
1975-01-01	49.5320203389268
1976-01-01	49.3354998041128
1977-01-01	49.1257463136332
1978-01-01	48.9680532703159
1979-01-01	48.9411176017980
1980-01-01	49.0693716621760
1981-01-01	49.0296044435142
1982-01-01	49.1332953187247
1983-01-01	49.3383522455365
1984-01-01	49.5739798379547
1985-01-01	49.8051442583473
1986-01-01	49.8900283157242
1987-01-01	49.9644723937148
1988-01-01	50.0484181686708
1989-01-01	50.1665004908983
1990-01-01	50.3235129877174
1991-01-01	50.6689037862999
1992-01-01	51.0493636238489
1993-01-01	51.4402729614273
1994-01-01	51.8077725132607
1995-01-01	52.1347547431668
1996-01-01	52.4725421933231
1997-01-01	52.7613392742699
1998-01-01	53.0218677121709
1999-01-01	53.2891636895911
2000-01-01	53.5805334708117
2001-01-01	53.7421228552335
2002-01-01	53.9580242411785
2003-01-01	54.1980049185984
2004-01-01	54.4174631313632
2005-01-01	54.5975467063501
2006-01-01	54.7249590510649
2007-01-01	54.7893228680239
2008-01-01	54.8325421603490
2009-01-01	54.9050345192177
2010-01-01	55.0204873102658
2011-01-01	55.2427324403562
2012-01-01	55.5192182855248
2013-01-01	55.8079717806597
2014-01-01	56.0612642146736
2015-01-01	56.2650943916306
2016-01-01	56.3474616754992
2017-01-01	56.4156015874541