Year	Percent of Total
1960-01-01	21.5189179309084
1961-01-01	21.6097971901919
1962-01-01	21.4925935562594
1963-01-01	21.4068120254008
1964-01-01	21.4453341302418
1965-01-01	21.5661550502196
1966-01-01	21.5311416452287
1967-01-01	21.3928188365085
1968-01-01	21.3710560450112
1969-01-01	21.4966825592638
1970-01-01	21.6622523659827
1971-01-01	21.5589847483519
1972-01-01	21.3365799990292
1973-01-01	21.0238524754460
1974-01-01	20.6362088445442
1975-01-01	20.1906419333149
1976-01-01	19.8562670407086
1977-01-01	19.4829497652988
1978-01-01	19.0909804537248
1979-01-01	18.6879365974376
1980-01-01	18.2822200730041
1981-01-01	17.8700738868516
1982-01-01	17.4435870409835
1983-01-01	17.0544999847510
1984-01-01	16.7387677138306
1985-01-01	16.4960241540117
1986-01-01	16.3491828736227
1987-01-01	16.2263378097662
1988-01-01	16.1643280482245
1989-01-01	16.1413316132731
1990-01-01	16.1248587128833
1991-01-01	16.2967619801085
1992-01-01	16.4201661769461
1993-01-01	16.5482183743059
1994-01-01	16.7061875802042
1995-01-01	16.8862724407481
1996-01-01	16.9579296964006
1997-01-01	17.0613869539855
1998-01-01	17.1615384090925
1999-01-01	17.2093684616791
2000-01-01	17.1773407295344
2001-01-01	17.0108082487166
2002-01-01	16.8123471680108
2003-01-01	16.6149252160644
2004-01-01	16.4333746817262
2005-01-01	16.2501458255020
2006-01-01	16.1468621912220
2007-01-01	15.9584187894935
2008-01-01	15.7277844410176
2009-01-01	15.4934017641533
2010-01-01	15.2781346150231
2011-01-01	15.1597849180982
2012-01-01	15.0355110995426
2013-01-01	14.9173757553336
2014-01-01	14.8071105547681
2015-01-01	14.7027931459837
2016-01-01	14.6176332950450
2017-01-01	14.5408132402579