Year	Percent of Total
1960-01-01	57.2145870133126
1961-01-01	56.9224590360190
1962-01-01	56.6171598309151
1963-01-01	56.3503852241952
1964-01-01	56.2044817411229
1965-01-01	56.1972775382486
1966-01-01	55.9947063201202
1967-01-01	55.9170528898582
1968-01-01	55.9556400633144
1969-01-01	56.1480963841258
1970-01-01	56.5652578177251
1971-01-01	56.3182460071735
1972-01-01	56.3241451202215
1973-01-01	56.5302948889941
1974-01-01	56.7840520217054
1975-01-01	56.9465672365802
1976-01-01	57.0834357677027
1977-01-01	57.0957162605350
1978-01-01	56.9969527782891
1979-01-01	56.8184945644695
1980-01-01	56.4880054832077
1981-01-01	56.1057975361305
1982-01-01	55.8040307346095
1983-01-01	55.5045711105811
1984-01-01	55.2057760451483
1985-01-01	54.9721925014489
1986-01-01	54.3029168350956
1987-01-01	53.8197158696270
1988-01-01	53.4720599712671
1989-01-01	53.1904823995866
1990-01-01	52.9427475014408
1991-01-01	52.9478648462181
1992-01-01	52.9269600217951
1993-01-01	52.9376766324558
1994-01-01	53.0666748778585
1995-01-01	53.3332276957876
1996-01-01	53.7277742896456
1997-01-01	54.2402632216747
1998-01-01	54.7751525130013
1999-01-01	55.2542809583380
2000-01-01	55.6575286941885
2001-01-01	55.9769101634670
2002-01-01	56.3194864399684
2003-01-01	56.6139897007102
2004-01-01	56.8435894853459
2005-01-01	57.0282985856649
2006-01-01	57.3291156337216
2007-01-01	57.6398694363020
2008-01-01	57.9097853798516
2009-01-01	58.1543947878752
2010-01-01	58.4075979072741
2011-01-01	58.6116726508363
2012-01-01	58.8991067723353
2013-01-01	59.1838862611719
2014-01-01	59.4387050390287
2015-01-01	59.6837302373938
2016-01-01	59.7814963691884
2017-01-01	59.9591066894167