Year	Percent of Total
1960-01-01	56.5012458101180
1961-01-01	56.1852266237659
1962-01-01	55.7867276157444
1963-01-01	55.3692859910374
1964-01-01	55.0401515296276
1965-01-01	54.8505747772312
1966-01-01	54.5360350147011
1967-01-01	54.3855963180993
1968-01-01	54.3563477315022
1969-01-01	54.3890279277782
1970-01-01	54.4590988229727
1971-01-01	54.4360655977117
1972-01-01	54.4710205554735
1973-01-01	54.5524111019972
1974-01-01	54.6674448052514
1975-01-01	54.8009797763074
1976-01-01	54.8415929380928
1977-01-01	54.8660384066481
1978-01-01	54.8786736895678
1979-01-01	54.8768779645098
1980-01-01	54.8506232206378
1981-01-01	54.6208403946537
1982-01-01	54.3862768873335
1983-01-01	54.1476590911924
1984-01-01	53.9204743852447
1985-01-01	53.7237975970345
1986-01-01	53.3837617002293
1987-01-01	53.1629390480691
1988-01-01	53.0235062116305
1989-01-01	52.9252476172678
1990-01-01	52.8596149826501
1991-01-01	52.8797354719633
1992-01-01	52.8974986378051
1993-01-01	52.9600216712778
1994-01-01	53.1281991413321
1995-01-01	53.4206091557770
1996-01-01	53.7170112357548
1997-01-01	54.1204822366407
1998-01-01	54.5985745808280
1999-01-01	55.0985805289088
2000-01-01	55.5912249099331
2001-01-01	56.0105892770225
2002-01-01	56.4495837055857
2003-01-01	56.8944178120953
2004-01-01	57.3333583355868
2005-01-01	57.7606029058001
2006-01-01	58.1529837481589
2007-01-01	58.5162598414610
2008-01-01	58.8701486621009
2009-01-01	59.2464327652755
2010-01-01	59.6596749655512
2011-01-01	60.0193848154973
2012-01-01	60.4280017610682
2013-01-01	60.8567419392441
2014-01-01	61.2634460115549
2015-01-01	61.6277603124471
2016-01-01	61.9499316606274
2017-01-01	62.2276522964779