Year Percent of Total 1960-01-01 10.8243162485537 1961-01-01 10.9692824808390 1962-01-01 11.1024842299573 1963-01-01 11.2350017431762 1964-01-01 11.3747304240514 1965-01-01 11.5210457928102 1966-01-01 11.7499300581495 1967-01-01 11.9676148246551 1968-01-01 12.1780403413591 1969-01-01 12.3776909472786 1970-01-01 12.5646219249385 1971-01-01 12.7556059446097 1972-01-01 12.9164336444482 1973-01-01 13.0489727807728 1974-01-01 13.1544552933036 1975-01-01 13.2288838729544 1976-01-01 13.4228357321547 1977-01-01 13.5775333734483 1978-01-01 13.6783974431763 1979-01-01 13.7030064307352 1980-01-01 13.6408836440152 1981-01-01 13.6531233808778 1982-01-01 13.5870369051597 1983-01-01 13.4755888914742 1984-01-01 13.3662297188316 1985-01-01 13.2894865952181 1986-01-01 13.2683784238308 1987-01-01 13.2697168789311 1988-01-01 13.2936667040880 1989-01-01 13.3376223835470 1990-01-01 13.3973823374569 1991-01-01 13.5138422992504 1992-01-01 13.6386863365305 1993-01-01 13.7572137798947 1994-01-01 13.8497588418445 1995-01-01 13.9106061756858 1996-01-01 13.9971352587808 1997-01-01 14.0465838361422 1998-01-01 14.0696000544815 1999-01-01 14.0765938107230 2000-01-01 14.0737394606320 2001-01-01 14.1765750866655 2002-01-01 14.2635319994772 2003-01-01 14.3346403709185 2004-01-01 14.3876198212116 2005-01-01 14.4206953490505 2006-01-01 14.3326015886449 2007-01-01 14.2293805637826 2008-01-01 14.1256016738644 2009-01-01 14.0425043171281 2010-01-01 13.9930181594797 2011-01-01 13.9560065468967 2012-01-01 13.9419257044218 2013-01-01 13.9469563317735 2014-01-01 13.9640060684934 2015-01-01 13.9942231107331 2016-01-01 14.1484019890681 2017-01-01 14.3118149643074