Year	Percent of Total
1960-01-01	24.1465730181994
1961-01-01	24.3266269354417
1962-01-01	24.3706612286612
1963-01-01	24.3185933895060
1964-01-01	24.2184434704538
1965-01-01	24.0909708409463
1966-01-01	24.0665523164206
1967-01-01	24.0172245542527
1968-01-01	23.9508840374608
1969-01-01	23.8597110383759
1970-01-01	23.7305567289173
1971-01-01	23.6366324929058
1972-01-01	23.4874255217722
1973-01-01	23.2815197961555
1974-01-01	23.0078652440238
1975-01-01	22.6537459183457
1976-01-01	22.2093142183682
1977-01-01	21.7229093444896
1978-01-01	21.1797609283188
1979-01-01	20.5935934115368
1980-01-01	20.0027444591274
1981-01-01	19.4884134137423
1982-01-01	18.9986577409806
1983-01-01	18.5510957575510
1984-01-01	18.1520889615465
1985-01-01	17.8005750729838
1986-01-01	17.6003982700568
1987-01-01	17.3899464611233
1988-01-01	17.2004906679066
1989-01-01	17.0771797910760
1990-01-01	17.0446853805831
1991-01-01	17.0774694636711
1992-01-01	17.2053456771864
1993-01-01	17.3874571942655
1994-01-01	17.5523177331470
1995-01-01	17.6528116662689
1996-01-01	17.7262899521085
1997-01-01	17.7279280968842
1998-01-01	17.6644211691513
1999-01-01	17.5657956669670
2000-01-01	17.4494122571419
2001-01-01	17.2495812325543
2002-01-01	17.0350862807041
2003-01-01	16.8033184249961
2004-01-01	16.5514920078228
2005-01-01	16.2877035610396
2006-01-01	16.0142069533177
2007-01-01	15.7435930944011
2008-01-01	15.4866662315872
2009-01-01	15.2533468025287
2010-01-01	15.0513708490494
2011-01-01	14.9497611791354
2012-01-01	14.8588276161745
2013-01-01	14.7973348003375
2014-01-01	14.7749187721585
2015-01-01	14.7847734714750
2016-01-01	14.8265495988390
2017-01-01	14.8746962749550