Year	Percent of Total
1960-01-01	11.0370196066609
1961-01-01	11.2100147709342
1962-01-01	11.4012107023228
1963-01-01	11.6025603792411
1964-01-01	11.7967758905106
1965-01-01	11.9767064406332
1966-01-01	12.1800188687186
1967-01-01	12.3595327498872
1968-01-01	12.5233873138351
1969-01-01	12.6851965480591
1970-01-01	12.8522262297281
1971-01-01	13.0112932041301
1972-01-01	13.1724510483066
1973-01-01	13.3364656955839
1974-01-01	13.5027840494402
1975-01-01	13.6734471365117
1976-01-01	13.8956293955890
1977-01-01	14.1125229642487
1978-01-01	14.3246067004124
1979-01-01	14.5306697884636
1980-01-01	14.7291925064536
1981-01-01	14.9583566420174
1982-01-01	15.1563226212692
1983-01-01	15.3361126028437
1984-01-01	15.5133741942281
1985-01-01	15.6942095131233
1986-01-01	15.8731563549181
1987-01-01	16.0461221580867
1988-01-01	16.1975393999856
1989-01-01	16.3044748826465
1990-01-01	16.3559544509022
1991-01-01	16.3710211405582
1992-01-01	16.3353315397387
1993-01-01	16.2560450038316
1994-01-01	16.1442688953304
1995-01-01	16.0094756233978
1996-01-01	15.8893419366117
1997-01-01	15.7463969330325
1998-01-01	15.5880648078487
1999-01-01	15.4221140615878
2000-01-01	15.2564349607400
2001-01-01	15.1470271238265
2002-01-01	15.0349129645081
2003-01-01	14.9333954179619
2004-01-01	14.8568770396506
2005-01-01	14.8150490764543
2006-01-01	14.7689206453145
2007-01-01	14.7333868966499
2008-01-01	14.7242460246020
2009-01-01	14.7688919824825
2010-01-01	14.8873344770377
2011-01-01	15.1112409160410
2012-01-01	15.4076400930805
2013-01-01	15.7381151172687
2014-01-01	16.0463248235369
2015-01-01	16.3030334033612
2016-01-01	16.5924219374144
2017-01-01	16.8214811258678