Year	Percent of Total
1960-01-01	49.2557512916629
1961-01-01	48.6160323300722
1962-01-01	48.2179594598315
1963-01-01	48.0033658054278
1964-01-01	47.8784043135960
1965-01-01	47.7937996878377
1966-01-01	48.0182170853266
1967-01-01	48.2980074697578
1968-01-01	48.6243866703447
1969-01-01	49.0049280460233
1970-01-01	49.4316349188889
1971-01-01	49.5524562622129
1972-01-01	49.7294977031403
1973-01-01	49.9291254877422
1974-01-01	50.1076346426693
1975-01-01	50.2426422750426
1976-01-01	50.1140013277004
1977-01-01	49.9940291956197
1978-01-01	49.8760232944226
1979-01-01	49.7582966759352
1980-01-01	49.6384550323340
1981-01-01	49.2693364781247
1982-01-01	48.9663932995732
1983-01-01	48.7141352936594
1984-01-01	48.4842328320106
1985-01-01	48.2589601783106
1986-01-01	48.0147079937925
1987-01-01	47.7973913460686
1988-01-01	47.6641775408564
1989-01-01	47.7993572087026
1990-01-01	48.4025673464074
1991-01-01	48.8696224587369
1992-01-01	49.8756239134532
1993-01-01	51.4322508467980
1994-01-01	53.2181256083376
1995-01-01	54.6996851256006
1996-01-01	54.7887645932213
1997-01-01	54.4029313217165
1998-01-01	53.6194938874443
1999-01-01	52.8599060295613
2000-01-01	52.4808979350469
2001-01-01	52.8497830457538
2002-01-01	53.5047483044280
2003-01-01	54.3434558945001
2004-01-01	55.0914232203027
2005-01-01	55.5645489997203
2006-01-01	55.8053913613959
2007-01-01	55.8101052543334
2008-01-01	55.6687053964553
2009-01-01	55.5580656612925
2010-01-01	55.5749078594166
2011-01-01	55.5827932314265
2012-01-01	55.7168774104161
2013-01-01	55.9363265806314
2014-01-01	56.1712337478671
2015-01-01	56.3906282554454
2016-01-01	56.6432848209542
2017-01-01	56.8883884687003