Year	Percent of Total
1960-01-01	33.7392162496492
1961-01-01	33.8631225399681
1962-01-01	33.8671573021959
1963-01-01	33.7625202749905
1964-01-01	33.5664632229748
1965-01-01	33.2807903904017
1966-01-01	32.8409093175929
1967-01-01	32.2603624650889
1968-01-01	31.5813464487386
1969-01-01	30.8610985663601
1970-01-01	30.1337680129114
1971-01-01	29.2758587779301
1972-01-01	28.5031490948271
1973-01-01	27.7667223341987
1974-01-01	26.9960535401448
1975-01-01	26.1708080109313
1976-01-01	25.5074466117227
1977-01-01	24.7639911549307
1978-01-01	24.0044154092586
1979-01-01	23.3226091044308
1980-01-01	22.7624157093602
1981-01-01	22.3143317457096
1982-01-01	21.9669119555697
1983-01-01	21.7048295360211
1984-01-01	21.4859778630831
1985-01-01	21.2884473104589
1986-01-01	21.1508740815809
1987-01-01	21.0191200027881
1988-01-01	20.8963188963331
1989-01-01	20.7899710482620
1990-01-01	20.7000478104683
1991-01-01	20.6604970667087
1992-01-01	20.6411385147097
1993-01-01	20.6102175160772
1994-01-01	20.5302122345518
1995-01-01	20.3843099879090
1996-01-01	20.2622215038404
1997-01-01	20.0439251383215
1998-01-01	19.7584250901663
1999-01-01	19.4551801668385
2000-01-01	19.1620298601242
2001-01-01	18.8331651019580
2002-01-01	18.5420599013010
2003-01-01	18.2657279483756
2004-01-01	17.9752043675789
2005-01-01	17.6689250922479
2006-01-01	17.3919528162594
2007-01-01	17.1228214522065
2008-01-01	16.8736664241049
2009-01-01	16.6538388428164
2010-01-01	16.4636209992148
2011-01-01	16.3852194218982
2012-01-01	16.2678261083838
2013-01-01	16.1434380654704
2014-01-01	16.0433271671111
2015-01-01	15.9779262747301
2016-01-01	15.9708664319158
2017-01-01	16.0250139532062